Bega Valley Shire Council FINAL REPORT 6 March 2013

Ecological Assessment of the Potential Impacts on Merimbula Lake from Shallow Dunal Exfiltration of Effluent

Merimbula Effluent Management Options Investigation

AECOM Merimbula Effluent Management Options Investigation Ecological Assessment of the Potential Impacts on Merimbula Lake from Shallow Dunal Exfiltration of Effluent

Ecological Assessment of the Potential Impacts on Merimbula Lake from Shallow Dunal Exfiltration of Effluent Merimbula Effluent Management Options Investigation

Prepared for Bega Valley Shire Council

Prepared by

AECOM Australia Pty Ltd Level 21, 420 George Street, Sydney NSW 2000, PO Box Q410, QVB Post Office NSW 1230, Australia T +61 2 8934 0000 F +61 2 8934 0001 www.aecom.com ABN 20 093 846 925

6 March 2013

60102089

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6 March 2013 AECOM Merimbula Effluent Management Options Investigation Ecological Assessment of the Potential Impacts on Merimbula Lake from Shallow Dunal Exfiltration of Effluent

Quality Information Ecological Assessment of the Potential Impacts on Merimbula Lake from Shallow Document Dunal Exfiltration of Effluent 60102089

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Date 6 March 2013

Prepared by Kathryn Duchatel and Dr Mark Gibbs

Reviewed by Matthew Renshaw

Revision History

Authorised Revision Revision Details Date Name/Position Signature

A 14-Jun-2012 Draft for Review Matthew Renshaw

B 17-Aug-2012 Draft for Review Matthew Renshaw

C 06-Mar-2013 Final Matthew Renshaw Principal Engineer

6 March 2013 AECOM Merimbula Effluent Management Options Investigation Ecological Assessment of the Potential Impacts on Merimbula Lake from Shallow Dunal Exfiltration of Effluent

Table of Contents Executive Summary i 1.0 Introduction 1 1.1 Merimbula sewerage system 1 1.2 Options investigation 2 1.2.1 Effluent Disposal Options 3 1.3 Purpose of this study 3 1.4 Scope of works 3 2.0 Environmental setting 6 2.1 Merimbula Lake 6 2.1.1 Hydrodynamics 6 2.2 Protected ecological values 6 2.2.1 Seagrasses 7 2.2.2 Mangroves 7 2.2.3 Aquatic fauna 8 2.2.4 Oyster aquaculture 8 3.0 Relevant legislation 10 3.1 Overview 10 3.2 Environment Protection and Biodiversity Conservation Act 1999 10 3.2.1 Matters of National Environmental Significance 10 3.3 Threatened Species Conservation Act 1995 13 3.4 Fisheries Management Act 1994 14 3.4.1 Marine vegetation 14 3.4.2 Oyster aquaculture 15 3.5 Coastal protection under SEPPs 15 3.5.1 SEPP 71 - Coastal Protection 15 3.5.2 SEPP 14 - Coastal Wetlands 15 4.0 Shallow Dunal Exfiltration option 16 4.1 Background 16 4.2 Numerical modelling 16 4.2.1 Overview 16 4.2.2 Migration scenarios 16 4.3 Modelling results 17 4.3.1 Groundwater discharge 17 4.3.2 Nutrient transport simulation 18 4.4 Nutrient flux data 19 4.4.1 Simulated flux rates 19 5.0 Impact Assessment 25 5.1 Preamble 25 5.2 Potential near-field ecological impacts 25 5.2.1 Benthic micro and macro algal communities 25 5.2.2 Aquatic vegetation 28 5.3 Potential far-field ecological impacts 28 6.0 Approvals 30 6.1 EPBC Act 30 6.2 TSC Act 30 6.3 FM Act 30 6.4 Oyster aquaculture 30 6.5 State Environmental Planning Policies 30 7.0 References 32 Appendix A IGCC figures A Appendix B Government database search results B

6 March 2013 AECOM Merimbula Effluent Management Options Investigation Ecological Assessment of the Potential Impacts on Merimbula Lake from Shallow Dunal Exfiltration of Effluent

Appendix C Flora and Fauna of Merimbula Lake - 1984 C Appendix D Supplementary Report (Elgin Associates, 2013) D

List of Tables Table 1 Nationally threatened and migratory species recorded within or adjacent to the study area 11 Table 2 Threatened species, communities in NSW recorded within or adjacent to the study area 13 Table 3 Contaminant transport simulation scenarios 17 Table 4 Predicted phosphate and nitrate concentrations (Table 13.6 from IGGC 2013) 18 Table 5 Nutrient transport simulation scenarios 18 Table 6 Modelled Nutrient Fluxes from Groundwater in grams per day (Source: Table 13.10 IGGC (2013)) 19 Table 7 Modelled Nutrient Fluxes from Groundwater in µmol/m2/day (Source: Table 13.11 IGGC (2013)) 20 Table 8 Optima and tolerance ranges of diatoms along Argentinean coastline in mg/L 26 Table 9 Summary of nutrient flux data found 26

List of Figures Figure 1 Merimbula Sewerage System and Surrounds 2 Figure 2 Merimbula Lake Study Area 5 Figure 3 Ecological features of the study area 9 Figure 4 Scenario 2 modelled phosphate flux contour map 21 Figure 5 Scenario 2 modelled nitrate flux contour map 22 Figure 6 Scenario 3 modelled phosphate flux contour map 23 Figure 7 Scenario 3 modelled nitrate flux contour map 24 Figure 8 Comparison of water quality (Chl a µg/L) for NSW coastal lakes 29

6 March 2013 AECOM Merimbula Effluent Management Options Investigation i Ecological Assessment of the Potential Impacts on Merimbula Lake from Shallow Dunal Exfiltration of Effluent

Executive Summary Overview The Merimbula sewerage system services the Bega Valley Shire’s coastal towns of Merimbula, Pambula, South Pambula and Pambula Beach. Bega Valley Shire Council (BVSC) engaged AECOM Australia Pty Ltd (AECOM) to investigate, identify and assess options for the beneficial use of effluent and the disposal of the effluent remaining (i.e. excess effluent that is unable to be beneficially used) from the Merimbula sewage treatment plant (STP). The outcome of the options investigation is to form a strategy for effluent management that provides the greatest benefit to the community and environment, whilst being affordable. A range of investigations have been undertaken to identify options for the disposal of effluent from the STP including the construction of an exfiltration system within the Merimbula-Pambula dunal system to allow effluent to exfiltrate into the dunal aquifer. This option would result in groundwater near an exfiltration system being recharged by effluent in addition to rainwater and would increase the natural volume and flow of groundwater towards the ocean and the lake. Groundwater modelling and simulations undertaken by Ian Grey Groundwater Consultanting Pty Ltd (IGGC) has shown that a shallow dunal exfiltration system north of the existing ponds is a viable option for the disposal of effluent from Merimbula STP from a hydraulic loading perspective, both over the long term and during peak discharge times. The modelling for year 2025 estimated effluent disposal volumes via a 400 metre exfiltration trench located within BVSC land in the dunes east of Merimbula airport, predicts that the majority of effluent disposed would flow in groundwater towards the ocean (approximately 81%) and the remainder would flow westward with the natural groundwater flow towards Merimbula Lake. Further modelling was commissioned by BVSC to assess the potential for phosphorus and nitrogen in effluent to migrate in groundwater to Merimbula Lake and ocean (Merimbula Bay). Four scenarios were modelled with discharge flux rates and typical nitrogen and phosphorus concentrations in groundwater estimated for the identified discharge zones in the bay and lake for each scenario. The general aim of this study is to investigate and identify the potential ecological impacts to Merimbula Lake of the shallow dunal exfiltration option. The specific objectives of this study are to: - Identify aquatic habitats and protected ecological matters in Merimbula Lake. - Review and interpret modelled nutrient flux data for comparison against background data provided by the Environment Protection Authority (EPA) and additional data where appropriate as found in national and international literature. - Identify potential impacts associated with modelled nutrient fluxes on the receiving environment of Merimbula Lake. - Identify likely approvals pathways associated with the shallow dunal exfiltration option. Potential ecological impacts Under two of the four scenarios modelled (IGGC 2013 Scenarios 1 & 3) there are no simulated phosphate or nitrate plumes to the Merimbula Lake system. All of the phosphorus and nitrogen in the effluent is adsorbed and denitrified in the groundwater system before it reaches the lake. These scenarios have the least ecological impacts. Under the scenario that would potentially lead to the most impacts (IGGC 2013 Scenario 2), both dissolved nitrate N and phosphate P would be discharged into the lake at a maximum rate of 3,287 grams/day of dissolved P and 924 grams/day of dissolved N. Under this scenario, the maximum nutrient fluxes would likely lead to enhanced production of both micro-phyto-benthos (micro algae in the sediments) and more visible macro-algae in the near- field or vicinity of the discharge location. It could also be argued however, that the assumption that Scenario 2 is based upon, (i.e. the sediments between the modelled exfiltration trench location and the discharge area in Merimbula Lake have a very low capacity to sorb phosphate and zero capacity for nitrate decay), is unrealistic and therefore it is unlikely that the ecological impacts suggested for this scenario would occur to the same degree and extent as reported.

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Under Scenario 2, increased groundwater discharge fluxes with higher than natural concentrations of nitrate and/or phosphate may impact saltmarsh and mangrove vegetation located within the lakeshore zones where the highest concentrations of nutrients in groundwater are likely to be discharged. Little is reported in relation to the sensitivity of these estuarine communities to groundwater impacts although broad interactions are inferred in general information found through literature searches. If increased nutrients were to be discharged, seagrass meadows in the vicinity of the discharge site may be impacted. Seagrasses are known to respond to increased nutrients; particularly nitrogen through increased growth, which in turn may result in greater quantities of organic matter and hence carbon recycling in these areas. Whilst in some cases, increases in seagrass biomass is seen as advantageous, there are some examples of where excessive seagrass growth is considered to be a negative impact, for example at Tuggerah lakes (Dickenson et al, 2006). In terms of far-field impacts to the greater Merimbula lake system, under the Scenario 2 that leads to the highest nutrient discharge , it is estimated from available information (Roper et al. 2011), that the increased nutrient loading may lead to an overall increase in the mean chlorophyll-a concentration from 2.00 µg/L to 2.17 µg/L. This would mean that the trophic status of the lake system would remain within the oligotrophic or nutrient-deficient range. Approvals A number of statutory approvals will require consideration for the shallow dunal exfiltration option. TSC Act: Saltmarsh is listed as an endangered ecological community under the Threatened Species Conservation Act 1995. Consultation with NSW Environment Protection Authority’s (EPA) Threatened Species Unit is recommended as part of the options development. Where significant impacts are found likely to occur, a Species Impact Statement will need to be prepared. FM Act: Under the Fisheries Management Act 1994, approval is required to harm marine vegetation (e.g. seagrasses and mangroves). In accordance with NSW Department of Primary Industries’ (DPI) ‘Fish Habitat Protection Plan No.2 Seagrasses’ (DPI, 1997), the discharge of effluent within 50 metres of any seagrass bed will generally not be approved unless special circumstances exist, and effective compensation is provided. In this case the diffuse discharge of effluent in groundwater would arise from effluent discharged approximately 1,000 metres from seagrass beds and as such, consultation with DPI-Fisheries is recommended to understand whether FMA approval would be required. Council will also be required to take into consideration the provision of the NSW Oyster Industry Sustainable Aquaculture Strategy (DPI, 2006). The Director-General of the DPI requires written notice of any development application that may affect a priority oyster aquaculture area or oyster aquaculture outside such an area. SEPP 14 – Coastal Wetlands: Under State Environmental Planning Policy 14 it is likely that the option of shallow dunal exfiltration would be considered a designated development. This means the development application will require consultation and concurrence of the Director-General of the NSW Department of Planning and Infrastructure (DoPI) and an environmental impact statement and be placed on public exhibition for public comment. SEPP 71 – Coastal Protection: A consent authority must reject development applications that will result in effluent discharge that negatively affects water quality. Consultation with the DoPI should be facilitated if this option is to proceed further. Protected ecological values The ecological values of Merimbula Lake have been recognised by its listing on the Directory of Important Wetlands in Australia (ANCA, 1996). The lake supports extensive seagrass meadows, fringing mangrove, and saltmarsh areas, all of which are located within the receiving environment. Seagrasses, mangroves and saltmarsh are defined as ‘marine’ vegetation protected in NSW by the FM Act. Saltmarsh is listed as an endangered ecological community in NSW under the TSC Act. The lake fauna is both diverse and abundant, and includes popular estuarine recreational fish species and priority oyster leases. The immediate environment of the subject area (modelled discharge zone) provides habitat for a number of migratory wader bird species protected under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act) and one endangered species protected under both the EPBC Act and TSC Act.

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The subject is also wholly located within the boundary of SEPP 71 – Coastal Protection and partially located within the boundary of a SEPP 14 – Coastal Wetland

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1.0 Introduction

1.1 Merimbula sewerage system The Merimbula sewerage system services the Bega Valley Shire’s coastal towns of Merimbula, Pambula, South Pambula and Pambula Beach. The Merimbula STP is located immediately south of Merimbula Airport and adjacent to the Pambula Merimbula Golf Club (PMGC), approximately half way between Merimbula and Pambula, 3.5 km south of Merimbula Main Beach and 2.5 km north of Pambula Beach (Figure 1). A base population of approximately 7,500 EP (equivalent persons) contributes sewage to the system, predominantly residential with some commercial sources. Sewage inflows increase significantly during summer holiday periods, when the population can increase two-fold. The current total average inflow to the STP is approximately 700 megalitres (ML) per year. While the permanent population is relatively stable, an average inflow of 900 ML per year has been adopted for this study to allow for future growth potential and to ensure the long term viability and potential impacts of a disposal scheme are adequately assessed. A volume of 500 ML per year for disposal has been adopted, based on future beneficial reuse being approximately 40-50% of total STP inflow for an average rainfall year. The current strategy for management of effluent from the STP is to meet the demands of an existing automated and priority access irrigation scheme at the PMGC, with the remainder of effluent being released to the environment through existing dunal exfiltration ponds or through discharge to Merimbula Bay via an existing shore-based ocean outfall. Ocean Outfall The existing ocean outfall is a 250 mm pipeline from the STP transfer pumping station to a pipe head structure located in the hind dunes at the centre of the beach, between the estuary entrances of Merimbula Lake in the north and Pambula Lake in the south. The pipeline length is approximately 1 km from the STP to the discharge point on the beach. The effluent is discharged just above the normal high water mark (2 mAHD) from where it flows across the beach and into the ocean waters of Merimbula Bay. The pipeline originally extended into the surf zone but was damaged in a large storm event in the 1970s and has not been reinstated. The periodic occurrence of algae in the ocean waters of Merimbula Bay and the perception of a possible link to effluent disposal attracts media and community attention. Whilst no proven causative link between the algae and the effluent discharge has been established, Council considers the ongoing use of the shore-based ocean outfall inadequate to meet community expectations and has committed to finding an alternative through this investigation. Dunal Exfiltration Ponds The existing dunal exfiltration system consists of two ponds located in a disused quarry in the sand dunes east of the STP. The ponds were built and commissioned for effluent disposal in 1986. Use of the ponds for effluent disposal is determined by the groundwater level near the ponds and season. When the groundwater level at monitoring bore BH10 is below 1.5 mAHD, the ponds may be used. The groundwater level near the ponds is allowed to fall leading up to the summer peak tourist season to enable the ponds to be used instead of the outfall during this time. Once the groundwater level at BH10 rises towards 1.5 mAHD, as a result of dunal exfiltration and/or rainfall, the ponds are taken off-line and the groundwater level allowed to fall away again. Typically the exfiltration ponds have capacity to dispose of about 100 to 250 ML of effluent from the STP each year, depending on rainfall and groundwater levels. Use of the exfiltration ponds ceased in May 2000, due to concerns that the discharge was impacting on the health of the vegetation in the surrounding dune area. Since 2005, Council has recommissioned the exfiltration ponds to assist in effluent management during the peak summer loading period and to reduce Council’s reliance on the shore-based ocean outfall.

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Figure 1 Merimbula Sewerage System and Surrounds

1.2 Options investigation The 2002-2008 Bega Valley Sewerage Program (BVSP) proposed an upgrade of the STP and the development of a new irrigation scheme for the beneficial reuse of effluent. As a result, a chlorine disinfection system was added to the STP, two existing storage lagoons were upgraded and a pump station and pipeline constructed to deliver effluent to a new storage for irrigation of farmland on a property known as Oaklands on the Pambula River flats. The Oaklands reuse scheme alone however did not resolve the need to continue the disposal of the majority of effluent to the ocean outfall and dunal exfiltration ponds. BVSC thereafter engaged AECOM to investigate, identify and assess options for the beneficial use of effluent and the disposal of the effluent remaining (i.e. excess effluent that is unable to be beneficially used) from the Merimbula STP. The outcome of the options investigation is to form a strategy for effluent management that provides the greatest benefit to the community and environment, whilst being affordable. A ‘long list’ of options for beneficial reuse and disposal were identified through review of background reports, publicly available information and consultation with BVSC. A Focus Group was established by BVSC, comprising agency, council, stakeholder and community representatives to assist with reviewing the options and direction of the investigations. The Focus Group reviewed and short-listed the long-list of options at a facilitated workshop in April 2011. At this workshop the Focus Group: - Ruled out any options that did not meet the fundamental project objectives and guided further development of preliminary criteria for use in consultation during further Focus Group workshops. - Short-listed options for beneficial reuse that are largely focused around irrigation, given that there is minimal industry and/or commercial end recipients in the study area. Irrigation options investigated include

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agricultural areas (located in South Pambula, Lochiel, Millingandi, and Wolumla) and urban open space areas (located in Pambula). 1.2.1 Effluent Disposal Options A range of investigations have been undertaken to identify options for the disposal of effluent from the STP. The receiving environments that exist in the study area that have been considered for effluent disposal include: - Merimbula Bay (ocean) - Shallow dunal aquifer - Deep alluvial aquifer - Pambula River - Panboola Wetlands - Merimbula or Pambula Lake. The ‘shallow dunal aquifer disposal’ option is the subject of this assessment. Shallow Dunal Exfiltration A sufficiently sized exfiltration trench or string of shallow injection wells or bores could be constructed within the Merimbula-Pambula dunal system to allow effluent to exfiltrate into the dunal aquifer. Any shallow dunal exfiltration option would need sufficient capacity to cater for future volumes of effluent unable to be beneficially used. IGGC (2013) has investigated characteristics of the dunal aquifer hydrogeology and assessed the impacts of a future shallow dunal exfiltration loading on groundwater levels, groundwater flow paths, groundwater quality and on the water quality of the receiving environments Merimbula Lake and the ocean. Options assessed included a 400 m exfiltration trench, or an equivalent line of 9 injection wells at 50 m spacing, in three locations in the dunes: central, BVSC land area and north (near Fishpen). The results of the IGGC (2013) investigation indicate that the three potential disposal areas are all expected to be viable from a hydraulic loading perspective, with the preferred disposal area being the central part of the dune system due to the greater area and volume of the dunes in this area and the longer groundwater travel times to Merimbula Lake. Further modelling by IGGC (2013) assessed the potential for phosphorus and nitrogen in effluent to migrate in groundwater to Merimbula Lake and the ocean (Merimbula Bay) from the modelled exfiltration trench located in the BVSC land area. Four scenarios were modelled with discharge flux rates and typical nitrogen and phosphorus concentrations in groundwater estimated for the identified discharge zones in the bay and lake, for each scenario.

1.3 Purpose of this study During consultation for the options study (8 November 2011), the EPA raised concerns in relation to the potential for shallow dunal exfiltration of effluent to increase the flux of nutrients to Merimbula Lake within the modelled groundwater discharge area and: - exhaust the existing phosphorus sink in benthic sediments within this area - increase benthic micro-phyto-benthos (MPB) productivity within this area. This feedback from the EPA resulted in BVSC engaging AECOM to conduct an additional assessment in relation to the potential impacts of the ‘shallow dunal aquifer disposal’ option on the ecology of Merimbula Lake within the identified groundwater discharge area.

1.4 Scope of works This study aims to provide a high level assessment of the potential ecological impacts of the shallow dunal exfiltration option. The focus of this report is on the near field environment where the groundwater discharge is likely to occur although some consideration of the far-field impacts is presented. The scope of works was determined in consultation with BVSC and EPA and includes the following: 1) Background review and compilation of available data.

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2) Identification and delineation of aquatic habitats and communities, with consideration to threatened species, communities and populations, and / or other matters protected under national and state environmental legislation that are found to occur, or are likely to occur within the study area. 3) Review and interpretation of modelled nutrient flux data for comparison against natural background benthic fluxes in other estuarine environments provided by EPA and additional data where appropriate as found in national and international literature. 4) Consult with EPA relating to assessment of biogeochemistry data and interpretation. 5) Identify potential impacts and the potential significance of any such impacts. 6) Identify approvals pathways that would be required in proceeding with shallow dunal exfiltration as a part of BVSC’s effluent management strategy. Figure 2 shows the simulated groundwater discharge zones for the ocean and Merimbula Lake as identified through modelling undertaken by IGGC (2013) for an exfiltration trench located in the BVSC land area. The majority of effluent disposed by an exfiltration trench in the location shown will flow in groundwater towards the ocean. The focus of this assessment is on the ecological impacts within the predicted discharge zones in Merimbula Lake. This is due to the more confined environment of the lake and potential sensitivities of seagrass beds and the habitat they provide as well as oyster aquaculture areas. The ‘subject area’ relevant to this assessment therefore is limited to the simulated groundwater discharge zones identified within Merimbula Lake through modelling by IGGC (2013), although some consideration is given to impacts on the wider Merimbula Lake system. For the purposes of identifying approvals pathways associated with the shallow dunal exfiltration option, the following additional areas have also been considered: - The ‘study area’ which includes the subject area and any additional areas which may potentially be affected by modelled discharge scenarios into Merimbula Lake. - The ‘locality’ is the area within 10 km of the study area, also referred to as the search area for the purpose of data searches in government threatened species databases. This study has utilised the following data sources: - Groundwater modelling and simulations to identify discharge zones and forecast potential increased nutrient fluxes to Merimbula Lake undertaken by IGGC (2013). - Mapping of ecological values within the areas of simulated discharge zones. - Field surveys, algal sampling and identification, literature reviews and interpretations of Elgin and Associates (2013) - Appendix D - Consultation with EPA and data provided by the EPA relating to nutrient sediment fluxes collected from estuaries throughout NSW. - Additional nutrient flux data and relevant research and case studies found through scientific literature review.

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Figure 2 Merimbula Lake Study Area

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2.0 Environmental setting

2.1 Merimbula Lake Merimbula Lake is an inlet/lake system comprising a natural entrance and substantial marine delta which opens out into two basins. The lake entrance is permanently open. Merimbula is located on the northern shore of the lake inlet. The shoreline of the larger medium-depth basin consists of areas of rocky shoreline whilst the shoreline of the smaller shallow basin on the southern side of the estuary is predominantly mangrove lined and sand based. The northern and southern sides of the Lake’s entrance are connected via a 250 metre long causeway and short bridge. The ecological values of the lake have been recognised by its listing on the Directory of Important Wetlands in Australia (ANCA, 1996). The Directory describes wetlands that have qualified as nationally important, based on a range of criteria. The lake is included on the Directory under ‘Type A Marine and Coastal Zone wetlands’, as it provides a good example of the following wetland types within the South East biogeographic region: - Subtidal aquatic beds; includes seagrasses. - Estuarine waters; permanent waters of estuaries and estuarine systems of deltas. - Intertidal mud, sand or salt flats. - Intertidal marshes; includes saltmarshes, salt meadows, saltings, raised salt marshes, tidal brackish and freshwater marshes. - Intertidal forested wetlands; includes mangrove swamps, nipa swamps, tidal freshwater swamp forests. 2.1.1 Hydrodynamics

The Merimbula Lake and estuary system is recognised for its high ecological, amenity and commercial values. The estuary is classified as a wave-dominated barrier estuary according to the Roy et al. (2001) classification. The average depth of the estuary is considered to be 2.6 m and volume of approximately 12,924 ML (Appendix D). The fact that the entrance is relatively wide and remains open allows for substantial flushing of the lake system. Roper et al (2010) estimates the flushing time of the lake system to be about 25.3 days and this acts to maintain a fair standard of water quality (3.3 out of 5; Appendix D; Roper et al. 2011). Figure 5 in Appendix D shows qualitative estimates of the relative residence times for different parts of the lake system. Inspection of this figure suggests that the location of the predicted discharge of nutrients into the lakes system will be in the region of the lower lake that is hydraulically closest to the ocean. However this southern section of the lake also contains the shallow, and largely enclosed embayments near the golf course that are likely to have longer flushing times by comparison with the larger parts of the lake system. Table 5 in Appendix D contains estimates of the averaged water depths at the site (0.3 m at averaged low tide).

2.2 Protected ecological values Merimbula Lake supports extensive seagrass meadows and the lake foreshores and tributary streams also support fringing mangrove, saltmarsh and freshwater wetland areas. The lake fauna is both diverse and abundant, and includes popular estuarine recreational fish species and oyster aquaculture operations. Studies conducted by Day and Hutchings(1984) found a diverse range of macrophytes, macroalgae, invertebrates, fish and bird species within the lake. A complete list of all species sampled and identified is provided in Appendix C. Estuary habitat mapping (Creese et al. 2009) indicates seagrass to cover 1.64 ha of the lake, with 0.35 ha and 0.59 ha of mangroves and saltmarsh respectively. All three communities are located within the subject area (the area of simulated groundwater discharge from exfiltration) (refer Figure 3). Seagrasses, mangroves and saltmarsh are defined as ‘marine’ vegetation protected in NSW by the FM Act. Further, saltmarsh is listed as an endangered ecological community in NSW under the TSC Act. Appendix D contains details of an investigation at the site and description of the vegetation.

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2.2.1 Seagrasses Seagrasses are aquatic flowering plants that form 'meadows' in near-shore brackish or marine waters, in temperate and tropical regions. Seagrasses are an important link in the critical chain of habitats required for sustainable fisheries production providing nursery habitat for an abundance of fish, crustaceans and molluscs, including many commercially valued species. With the exception of sea turtles and dugongs which graze directly on seagrasses, most of the carbon fixed by seagrasses enters the food web via detritivores rather than through direct consumption. A wide range of nutrient cycling processes occurs in coastal seagrass communities, and these vary according to seagrass species and the extent of grazing. Seagrasses can support high rates of nitrogen fixation, denitrification and sulfate reduction. Uptake of nutrients by seagrasses (and other benthic plants and algae) can also change the status of sediment from a nutrient source to a nutrient sink. Seagrass meadows also have the potential to influence physical and chemical parameters in the water column (OzCoasts 2012). Seagrasses also bind sediment which helps to stabilise shorelines against erosion and the baffling effect of seagrasses on water movement causes the deposition of suspended sediment and organic matter. Baffling can also impede the mixing process which destabilises water column stratification, thereby influencing the dissolved oxygen status of bottom waters (OzCoasts 2012). There are several species of seagrass known to occur within the lake including: - Varieties of Eelgrass (Zostera Capricornia, Z. muelleri and Heterozostera tasmanica) - Strapweed (Posidonia australis) - Varieties of Paddleweed (Halophila ovalis, and H.decipiens). The site investigation of the site (Appendix D) identified three species of seagrass: Zostera muelleri (eelgrass), Posidonia australis (strapweed), and Halophila ovalis (paddleweed). It was also highlighted that Posidonia occurs in only five locations in the Bega Valley, including Merimbula Lake. Appendix D also details that over 60% of the site has seagrass coverage. 2.2.2 Mangroves Mangroves occur in the seaward edge of the intertidal zone and are inundated by tides on a daily basis. In order to survive in this environment, mangroves have developed specialised root-like structures (pneumatophores), which protrude from the substrate, usually higher than the mean high tide, and act like ‘breathing tubes’ facilitating oxygen transport within the plant. Mangrove pneumatophores provide both habitat, and protect shorelines from erosion (in combination with the mangrove tree or shrub itself). Mangrove root systems are efficient at dissipating wave energy (Massel et al 1999). Likewise, they slow down tidal water enough that its sediment is deposited as the tide comes in, which are not re-suspended when the tide leaves, except for fine particles (Mazda et al 1997). As a result, mangroves build their own environment (Mazda et al 2005). Mangroves provide important habitats for fish, crabs, birds and other animals, providing large amounts of organic matter, which is eaten by many small aquatic animals. In turn, these detritivores provide food for larger carnivorous fish and other animals. Mangrove forests are nursery grounds, feeding areas and shelter sites for fish and support many bird species, including migratory shorebirds which often use mangrove forests as roost sites, and sometimes as foraging sites. Additionally mangrove pneumatophores provide crustacean (e.g. oyster) habitat. Mangrove communities in the lake are dominated by Grey mangrove (Avicennia marina), and less commonly River mangrove (Aegiceras corniculatum). Appendix D details that a continuous band of grey mangroves (Avicennia marina) were found at the site. The site inspection (Appendix D) revealed that a saltmarsh community is present between the shoreline and the band of grey mangroves. Saltmarsh communities typically occur within the intertidal zone from the mean high water (MHW) level and the highest astronomical tide (HAT) and are flooded by larger tides less frequently than mangrove communities (average tidal range 1.6 - 2.0m+). Saltmarshes are characterised by plant species adapted to surviving in saline, often hypersaline environments, and provide habitats for a wide range of infaunal and epifaunal invertebrates, and low-tide and high-tide visitors such as crabs, shorebirds and fish. Saltmarshes have been found to play an important role as habitat for juvenile

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species of fish. Common galaxias (Galaxias maculatus) deposit their eggs in saltmarsh vegetation and saltmarsh crab larvae are a significant food source for carnivorous fish species. Specific types of crab species are reliant on larger tidal events in which large volumes of larvae are released from the saltmarsh environment (Mazumder 2004). 2.2.3 Aquatic fauna Fauna that inhabit the lake are numerous – stingrays, stingarees, soldier crabs, birds, fish, worms, eels, seahorses, flutemouths, shrimps, prawns, marine slaters, sea slugs and many recreational fish species. The lake is a popular recreational fishing area and fishing is an important part of the local economy. Records from weekly fishing reports over two years (Merimbula Big Game and Lakes Angling Club, October 2009 to October 2011) indicate the most frequently caught species are Dusky Flathead, Bream, Whiting, Trevally and Tailor. Salmon, Estuary Perch, Mullet, Garfish, Greasy-back and King prawns and calamari are also commonly reported. 2.2.4 Oyster aquaculture The lake supports a small but significant oyster farming industry. In 2005/2006, Merimbula Lake produced over 3% of the total NSW production of Sydney Rock Oyster (total value in excess of $1 million). Saccostrea glomerata (Sydney rock oyster) and Crassostrea gigas (Pacific oyster) are farmed in the Lake and the area also produces Angasi oysters. Areas in the lake that have been leased for oyster aquaculture cover 142.5 ha, with areas currently mapped as priority oyster aquaculture areas covering 125.8 ha1 (Figure 3).

1 does not include 16.4 ha sub-let from the lessees of the Merimbula Airport

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Figure 3 Ecological features of the study area

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3.0 Relevant legislation

3.1 Overview A component of the assessment is to identify statutory approvals that may be required in relation to the option of disposing effluent via shallow dunal exfiltration. The key relevant legislation in relation to the assessment of aquatic ecology of the lake are summarised below: - Commonwealth legislation x Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act). - State legislation x Threatened Species Conservation Act 1995 (TSC Act) x Fisheries Management Act 1994 (FM Act). - State Environmental Planning Policies x State Environment Planning Policy No. 71 Coastal Protection (SEPP 71) x State Environment Planning Policy No. 14 Coastal Wetlands (SEPP 14). As required by commonwealth and state impact assessment guidelines, searches of government databases were undertaken to identify protected matters that have the potential to occur within the locality. The following databases were searched for the assessment: - The Department of Sustainability, Environment, Water, Population and Community (SEWPaC) Protected Matters on-line search tool for matters of National Environmental Significance (NES) protected under the EPBC Act. - NSW Wildlife Atlas (OEH) database for threatened species listed under the TSC Act. - Department of Primary Industries - Fisheries threatened species database for threatened and protected species listed under the FM Act. As the focus of this assessment is limited to the area in which simulated groundwater discharge would occur in the Merimbula Lake (IGGC 2013), a large number of results returned from database searches are not relevant to this assessment. Threatened and/or otherwise protected species, populations, or communities that are relevant to this assessment typically occur within shallow tidal areas of estuaries. All lists generated from database searches are provided in Appendix B. Matters of ecological significance relevant to the study area are discussed in the following sections. Additional sources of information were also searched to gain an understanding of local populations of estuarine flora and fauna. These included local fishing club weekly reports, diving and photographic records found in locally based websites, BVSC’s Statement of Environment (SoE) reporting, government marine audits and related reporting.

3.2 Environment Protection and Biodiversity Conservation Act 1999 3.2.1 Matters of National Environmental Significance Approval under the EPBC Act is required from the Commonwealth Environment Minister if SEWPaC determines the proposal to be a controlled action that would have or is likely to have a significant impact on a matter of NES. The EPBC Act provides protection for eight matters of NES, two of which relate to the locality: - Threatened Species: 59 (29 birds, 1 fish, 4 frogs, 14 mammals, 3 sharks, 4 turtles, 4 plants). - Migratory Species: 47 (33 birds, 6 mammals, 4 turtles, 4 sharks). Of the listed threatened and migratory species, only 10 bird species (one endangered, two vulnerable and seven migratory species) have been recorded within or near the study area (Table 1). The remaining species are either terrestrial, rely on freshwater habitats, or require other habitat features that are not present within the study area (e.g. pelagic or deeper sea species which are highly unlikely to visit the shallower waters of the estuary).

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Table 1 Nationally threatened and migratory species recorded within or adjacent to the study area

Species name Common name Status Likelihood of occurrence BIRDS Ardea ibis Cattle Egret Migratory Recorded in study area Ardenna pacificus Wedge-tailed Shearwater Migratory Recorded from Merimbula Bay Recorded near Pambula Beach & at Ardenna tenuirostris Short-tailed Shearwater Migratory Berrambool Botaurus poiciloptilus Australasian Bittern Endangered Recorded from subject area Diomedea exulans Vulnerable, Gibson's Albatross Recorded from Merimbula Bay gibsoni Migratory Gallinago hardwickii Latham's Snipe Migratory Recorded from subject area Haliaeetus leucogaster White-bellied Sea-Eagle Migratory Recorded from subject area Hydroprogne caspia Caspian Tern Migratory Recorded from Tura Beach Numenius Eastern Curlew Migratory Recorded from subject area madagascariensis Numenius phaeopus Whimbrel Migratory Recorded in study area Thalassarche cauta Shy Albatross, Vulnerable, Recorded near Pambula Beach (sensu stricto) Tasmanian Shy Albatross Migratory

Of the recorded species listed in Table 1, five bird species are considered as having a high likelihood of occurring within the subject area – due to the presence of habitat and / or database records either within or in close proximity to the subject area. These species are listed below along with a brief summary of habitat requirements sourced from Commonwealth threatened species profiles (relevant to the subject area). - Botaurus poiciloptilus Australasian Bittern (Endangered) Recorded within the subject area, and described as: x Occurring mainly in densely vegetated freshwater wetlands and, rarely, in estuaries or tidal wetlands (the latter mainly in the temperate southeast and southwest). x Brackish water is tolerated in estuaries and tidal wetlands, where birds inhabit beds of rushes or reeds in saltmarsh, especially near mouths of creeks or freshwater seepage; sea coasts are avoided. x Appears to be capable of moving between habitats as suitability changes. Based on the above factors, the subject area provides additional habitat for the species (i.e. by description not preferred habitat), and recorded evidence within the subject area indicate any impacts resulting from shallow dunal exfiltration must consider potential risks to the species. - Ardea ibis Cattle Egret (Migratory) Recorded in close proximity to the subject area (i.e. immediately downstream of the causeway and short bridge), and described as: x Occurs in tropical and temperate grasslands, wooded lands and terrestrial wetlands. x Commonly associated with the habitats of farm animals, particularly cattle, but also pigs, sheep, horses and deer known to follow earth-moving machinery and has been located at rubbish tips. x Uses predominately shallow, open and fresh wetlands including meadows and swamps with low emergent vegetation and abundant aquatic flora. x Roosts in trees, or amongst ground vegetation in or near lakes and swamps. It has also been recorded roosting near human settlement and industrial areas in Murwillumbah, NSW (Marchant & Higgins 1990). x Breeds in colonies in wooded swamps such as mangrove forests (e.g. the lower Adelaide River, Northern Territory), Melaleuca swamps (e.g. Shortland, NSW) and the eucalypt/lignum swamps of the Murray-Darling Basin.

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Based on the above factors, the subject area provides habitat for the species (i.e. mangrove forests), and recorded evidence within the subject area indicate any impacts resulting from shallow dunal exfiltration must consider potential risks to the species. - Gallinago hardwickii Latham's Snipe (Migratory) Recorded within the subject area, and described as: x Usually inhabiting open, freshwater wetlands with low, dense vegetation (e.g. swamps, flooded grasslands or heathlands, around bogs and other water bodies). x Sometimes occur in habitats that have saline or brackish water, such as saltmarsh, mangrove creeks, around bays and beaches, and at tidal rivers. These habitats are most commonly used when the birds are on migration. x Also occur in various sites close to humans or human activity (e.g. near roads, railways, airfields, commercial or industrial complexes). x Foraging habitats are characterised by areas of mud (either exposed or beneath a very shallow covering of water) and some form of cover (e.g. low, dense vegetation). x Roost on the ground near (or sometimes in) their foraging areas, usually in sites that provide some degree of shelter, e.g. beside or under clumps of vegetation, among dense tea-tree, in forests, in drainage ditches or plough marks, among boulders, or in shallow water if cover is unavailable. Based on the above factors, the subject area provides habitat for the species and recorded evidence within the subject area indicate any impacts resulting from shallow dunal exfiltration must consider potential risks to the species. - Haliaeetus leucogaster White-bellied Sea-Eagle (Migratory) Recorded in subject area, but as a wide ranging species records are likely to be aerial based and not necessarily associated with the immediate physical environment of the subject area. Therefore any impacts as a result of shallow dunal exfiltration are unlikely to cause any significant risk of threats to this species. - Numenius madagascariensis Eastern Curlew (Migratory) Several records within the subject area were found in government databases, and described as: x Most commonly associated with sheltered coasts, especially estuaries, bays, harbours, inlets and coastal lagoons, with large intertidal mudflats or sandflats, often with beds of seagrass. x Often recorded among saltmarsh and on mudflats fringed by mangroves, and sometimes use the mangroves. x Mainly forages on soft sheltered intertidal sandflats or mudflats, open and without vegetation or covered with seagrass, often near mangroves, and in saltmarsh. x Roosts on sandy spits and islets, especially on dry beach sand near the high-water mark, and among coastal vegetation including low saltmarsh or mangroves. x Also recorded roosting in trees and on the upright stakes of oyster-racks. - Numenius phaeopus Whimbrel (Migratory) Recorded in close proximity to the subject area (i.e. immediately downstream of the causeway and short bridge), and described as: x Often found on the intertidal mudflats of sheltered coasts, also found in harbours, lagoons, estuaries and river deltas, often those with mangroves, but also open, unvegetated mudflats. x Also use saltflats with saltmarsh, or saline grasslands with standing water left after high spring-tides. x Generally forage on intertidal mudflats, along the muddy banks of estuaries and in coastal lagoons, either in open unvegetated areas or among mangroves and sometimes forage on sandy beaches or among rocks. x Prefer mudflats with a 10–50% cover of Zostera, followed by areas of sand, mud bare mudflats, and rock platforms.

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x The Whimbrel is one of a small group of shorebird species that regularly roost in mangroves and other structures flooded at high tide, often roosting in the branches of mangroves around mudflats and in estuaries and occasionally in tall coastal trees. x They have also been observed to roost on the ground (sometimes under mangroves or in shallow water), on muddy, sandy or rocky beaches; rocky islets and coral cays. x Have been once recorded perched on upright stakes attached to oyster racks.

3.3 Threatened Species Conservation Act 1995 The TSC Act outlines the protection of threatened species, populations, ecological communities and critical habitat in NSW. The Act is administered by the NSW Office of Environment & Heritage (OEH). Under section 5A of the EP&A Act, an assessment of significance (7-part test, (DECC) 2007) may be required to determine the likely significance of impacts on threatened species, populations or ecological communities. NSW database searches returned the following state protected matters for the search area: - Endangered Ecological Community (EEC): one relevant to study area, Coastal Saltmarsh - Threatened Species: 42 (24 birds, 1 frog, 13 mammals, 4 plants) Of these species, those that have been recorded within the study area or in close proximity to the subject area are listed in:

Table 2 Threatened species, communities in NSW recorded within or adjacent to the study area

Species name Common name Status Likelihood of occurrence VEGETATION

Coastal Saltmarsh EEC Mapped in subject area BIRDS Botaurus poiciloptilus Australasian Bittern Endangered Recorded from subject area Haematopus fuliginosus Sooty Oystercatcher Vulnerable Recorded in study area Haematopus longirostris Pied Oystercatcher Endangered Recorded from subject area Thinornis rubricollis Hooded Plover Endangered Recorded in study area MAMMALS Dugong dugon Dugong Vulnerable Recorded from Merimbula Bay

- Coastal Saltmarsh Present within the subject area (Figure 3). The increased fresh groundwater and nutrient fluxes along the lakeshore may affect this community. - Botaurus poiciloptilus Australasian Bittern (Endangered) Discussed under Commonwealth EPBC Act (refer Section 3.2). - Dugong dugon Dugong One record was returned for the dugong, which was recorded as a dead specimen found on the beach in Merimbula Bay in 1993. Dugongs are found in abundance throughout north Australian waters, and considered occasional visitors NSW coastal and estuarine waters. Occurrence of the dugong in NSW (in the summer of 2002 / 2003) was associated with warmer water temperatures and large seagrass beds around Wallis Lake, Port Stephens, Lake Macquarie and Brisbane Water (SEWPaC, 2012). While the lake provides an abundance of seagrasses for this species, it is considered highly unlikely that the lake’s estuarine habitat is of significance to the species due to the following reasons: x the study area is considerably further south than past sightings of this species in NSW (as reported by SEWPaC.

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x lack of recent records within proximity to the subject area, both in scientific literature and anecdotally. - Haematopus fuliginosus Sooty Oystercatcher Recorded in close proximity to the subject area (i.e. immediately downstream of the causeway and short bridge), and described as: x Inhabiting marine littoral habitats, including islands, within 50 m of the shoreline. x Typically occupies rocky intertidal shorelines, e.g. at the base of cliffs and headlands, rock platforms, reefs, outcrops, rock stacks; also sandy beaches near intertidal mudflats or rocks; and occasionally estuaries. x Habitat is frequently disturbed by human activities around beaches, headlands and islands. x Nest is typically a scrape in sand, gravel, shingle or among rocks above the tideline, usually in bare areas though sometimes amongst wrack. x Forages in the intertidal zone mostly for marine invertebrates, especially molluscs, crustaceans and other hard-shelled animals, and above the tideline (on beaches, around stranded seaweed) for other invertebrates at high tide. - Haematopus longirostris Pied Oystercatcher Several records within the subject area, and described as: x Occupies muddy, sandy, stony or rocky estuaries, inlets and beaches, particularly intertidal mudflats and sandbanks in large marine bays. x Habitat of this species is frequently disturbed by human activities on beaches. x Nest is typically a scrape in sand, soil, shingle or shellgrit above the tideline, on a beach, lagoon shore, sandbank or sand island in an estuary, between high-water mark and dunes, amongst vegetation or wrack (e.g. seaweed, driftwood) or under a shrub, and lined with plant fibres or shells. x Forages in the intertidal and wave-wash zone mostly for marine invertebrates, especially bivalve molluscs. - Thinornis rubricollis Hooded Plover Recorded in close proximity to the subject area (i.e. immediately downstream of the causeway and short bridge), and described as: x Found most often on long stretches of sandy shore, backed by tussock and creeper-covered dunes with nearby inland lakes. x Preferred habitat has a wide wave wash zone with beach cast seaweed for feeding, backed by sparsely vegetated sand dunes for shelter and nesting. x Individuals also regularly use near-coastal saline and freshwater lakes and lagoons. x Forages on beaches, in wave-wash, lagoons and saltpans. Based on the above factors the subject area is not likely to provide important habitat for the species.

3.4 Fisheries Management Act 1994 The FM Act provides for the conservation, protection and management of fisheries, aquatic systems and habitats in NSW. The DPI manages the majority of the FM Act, although the EPA has some responsibilities relating to endangered species and habitats. The FM Act applies in relation to all waters that are within the limits of the State, and regulates certain activities that have the potential to impact on aquatic habitats. 3.4.1 Marine vegetation Under the Part 7 Division 4 of the FM Act, it is an offence to harvest or harm marine vegetation, which includes seagrass, mangroves and saltmarsh. Saltmarsh is also protected as an EEC under the TSC Act (as discussed above).

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To assist in the management of seagrasses, development that has the potential to impact on seagrasses is detailed within ‘Fish Habitat Protection Plan No.2 Seagrasses’ (DPI,1997) Under this plan, the discharge of effluent within 50 m of any seagrass bed will generally not be approved unless special circumstances exist, and effective compensation is provided. The three locations investigated and modelled (IGGC 2013) for a potential shallow dunal exfiltration of effluent (IGGC, 2013) are all located approximately 1,000 m from the nearest seagrass beds. 3.4.2 Oyster aquaculture Council would be required to take into consideration the provisions of the NSW Oyster Industry Sustainable Aquaculture Strategy (DPI, 2006), in particular the assessment of any development activities that may influence priority oyster aquaculture areas, which includes all oyster leases in Merimbula Lake. Examples of potential land use incompatibility issues include access to oyster leases being limited by the development or the risk of adverse impacts of the development on water quality and, consequently, on the health of oysters and on the health of consumers of those oysters.

3.5 Coastal protection under SEPPs There are a number of State Environmental Planning Policies (SEPPs) which regulate development in coastal areas. Their provisions are to be considered by authorities in conjunction with the relevant sections of the Coastal Protection Act 1979 and the Environmental Planning and Assessment Act 1979 when an application for development in the coastal zone is being assessed. 3.5.1 SEPP 71 - Coastal Protection SEPP 71 Coastal Protection is the main SEPP controlling development in the coastal zone. The subject area lies wholly within the coastal area for which SEPP 71. As with all other SEPPs, it is legally enforceable. SEPP 71 provides that a consent authority must reject development applications that will: - Impede or diminish access to coastal foreshores. - Result in effluent discharge that negatively affects water quality. - Involve a discharge of untreated storm water into the sea, a beach, an estuary, or coastal lake or creek. 3.5.2 SEPP 14 - Coastal Wetlands SEPP 14 Coastal Wetlands aims to protect and preserve coastal wetlands. A number of SEPP 14 wetland areas are mapped within the Lake, and one is located within the modelled groundwater discharge zone as shown in Figure 3. Under SEPP 14, a person must not clear land, construct a levee, drain land or fill land which is covered by the SEPP except with the consent of the local council and the concurrence (agreement) of the Director-General of Planning. Activities on SEPP 14 wetlands which require development consent are deemed to be designated development, which means the development application must be accompanied by an environmental impact statement and be placed on public exhibition for public comment.

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4.0 Shallow Dunal Exfiltration option

4.1 Background Potential dunal disposal options for Merimbula STP effluent have been identified through consultation with BVSC and a number of previous investigations. The process of disposal via exfiltration trenches or wells involves vertically downward migration of effluent directly beneath the exfiltration area and a progressive horizontal deflection of streamlines at the water table and at horizons of differing permeability. This recharging process establishes a localised groundwater mound, the geometry of which is constrained by the subsurface permeability distributions and regional flows. The key focus of this assessment is the potential impact that increased freshwater groundwater flow and increased nutrient concentrations in groundwater (above ambient or background sediment nutrient fluxes) could have on the ecology of Merimbula Lake. Detailed investigation of other potential contaminants in effluent (such as heavy metals, hydrocarbons, pesticides, faecal coliforms) is beyond the scope of works for this assessment, although considered broadly in relation to relevant approval pathways for this option (refer Section 6.0).

4.2 Numerical modelling 4.2.1 Overview IGGC (2013) has undertaken numerical groundwater modelling for three locations in the dunes between Merimbula Lake and Merimbula Bay to assess the potential for the disposal of effluent from Merimbula STP. The IGGC numerical model was developed using the following inputs: - Analysis of aquifer material for speciated carbon and phosphorus retention index relating to the potential for phosphorus sorption and retardation. - Analysis of available groundwater quality data from bores located near to the existing exfiltration ponds to determine nitrate decay (dentrification) and phosphorus sorption potential of the dune sediments. - Water level data for the Merimbula Lake. - Merimbula Lake and ocean bathymetry data, including the lateral extent of the lake and ocean areas underlain by the shallow aquifer. The addition of imaginary monitoring wells within the discharge zones to examine contaminant concentrations over time. The modelling showed that all three model exfiltration locations were viable for the disposal of effluent from a hydraulic loading perspective, both over the long term and during peak discharge times. In particular, the IGGC (2013) modelling for year 2025 estimated effluent disposal volumes from a 400 metre exfiltration trench located within the BVSC land area, predicted that the majority of effluent disposed would flow in groundwater towards the ocean (approximately 81%) and the remainder would flow westward with the natural groundwater flow towards Merimbula Lake. Further modelling was undertake to assess the potential for phosphorus and nitrogen in the effluent to migrate in groundwater to the ocean (Merimbula Bay) and Merimbula Lake from a 400 m exfiltration trench located within the BVSC land area. Four scenarios were modelled with discharge flux rates and typical nitrogen and phosphorus concentrations in groundwater estimated for the identified discharge zones in the bay and lake for each scenario. The results of the modelled scenarios are presented as contour maps of predicted final concentrations of phosphate and nitrate and time series graphs of concentration over time (refer Appendix A). Detailed discussion of the model’s development, application and modelling results are provided in IGCC (2013) and paraphrased herein.

4.2.2 Migration scenarios Four scenarios were modelled to examine existing (8.5 mg/L) and reduced (1.5 mg/L) phosphate concentrations present in discharged effluent from the STP, two Kd values for phosphorus sorption in the sediments and two R values for nitrate decay in the sediments. The parameter Kd is known as the partition (or distribution) coefficient

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and is an important parameter used to estimate the migration potential of contaminants present in aqueous solutions in contact with surface, subsurface and suspended solids (US EPA 1999). The parameter R represents a first-order decay reaction estimate and was used in the modelling to provide an estimate of nitrate removal by denitrification.

A Kd value of 2.0 for phosphate was obtained from testing of samples of aquifer material collected during the drilling and test production well installation program and is considered to provide a conservative estimate of the P sorption capacity of the dune material in the area assessed for the exfiltration trench modelling. A Kd value of 0.1 was also used to provide a worst-case estimate for phosphate removal. An R value of 0.002 day-1 was obtained from calibration of a simple numeric model of groundwater flow and total inorganic nitrogen concentrations in two groundwater monitoring bores near to the existing effluent ponds and is considered to provide a conservative estimate of the denitrification capacity of the dune material in the area assessed for the exfiltration trench modelling. An R value of 0 was also used to provide a worst-case estimate for nitrate removal and represents zero nitrate removal in groundwater. Table 3 provides a summary of the 4 scenarios contaminant transport scenarios used in the modelling.

Table 3 Contaminant transport simulation scenarios

Effluent Concentration (mg/L) Kd (mL/g) R (day-1) Scenario Phosphate as P Nitrate as N PO4 NO3

Scenario 1 8.5 2.5 2 0.002 Scenario 2 8.5 2.5 0.1 0 Scenario 3 1.5 2.5 2 0.002 Scenario 4 1.5 2.5 0.1 0

The above four scenarios are intended to represent a range of conservative best case and worst case parameters for phosphate and nitrate attenuation. Contaminant transport was simulated for a period of 21,000 days (57 years) for all scenarios. This encompasses the realistic lifespan of an exfiltration discharge system, which is likely to be 20 to 50 years (7,300 to 18,250 days). Scenario 2 assumes no denitrification capacity and very low phosphorus sorption capacity in the dunal sediments between the modelled exfiltration trench location and the groundwater discharge area in Merimbula Lake. The existence of these conditions is considered unlikely, based on available groundwater quality data collected from bores around the existing exfiltration ponds between 2004 and 2013 (showing that the concentration of phosphate and nitrate in groundwater is significantly lower than the concentration in the effluent disposed to the ponds) and analysis of dune sediment material (IGGC 2013) from 4 locations (providing a mean value Kd value of 11.6 mL/g rather than the very low 0.1 mL/g selected for this scenario). Hence it has been argued in IGGC (2013) that scenario 2 has a low likelihood of occurrence. Furthermore, BVSC intends to reduce phosphate in the effluent to < 1.5 mg/L at through alum dosing at the sewage treatment plant. Nevertheless, it is important to consider the worst case scenario to ensure extreme possible impacts are assessed.

4.3 Modelling results 4.3.1 Groundwater discharge Baseline groundwater flow was calculated through modelling of average rainfall conditions without exfiltration and thereafter with exfiltration simulated based on an estimated 2025 average daily effluent discharge loading of 1.4 ML/d. Under natural groundwater flow conditions the model shows the presence of a groundwater divide (recharge mound) extending from the southern area to close to the northern end of the exfiltration trench location. Under simulated groundwater flow conditions the groundwater divide becomes centred on the exfiltration trench with groundwater flowing directly towards the ocean (east-south-east) and towards the lake at its closest point (north-west) The greatest increase in overall net groundwater discharge occurs to the ocean, with a total net increase of 73% higher than under natural conditions. The total net increased discharge to the lake is 7.5% higher than under natural conditions. The time in which groundwater from the exfiltration trench will travel to the lake shore is estimated to be around 7 years, with typical travel times of 12 years or more prior to lake bed

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discharge. There is a clear decrease in groundwater velocity once the lake shore is reached reflecting the low hydraulic gradient in the shallow aquifer beneath the lake.

4.3.2 Nutrient transport simulation Typical nutrient concentrations from the model are summarised in Table 4 and predicted phosphate and nitrate concentration distributions are shown in figures from IGCC (2013) provided in Appendix A.

Table 4 Predicted phosphate and nitrate concentrations (Table 13.6 from IGGC 2013) Lake Lake Shore Lake Shore Lake Shore Lake Near Lake Near Scenario Shore Central Central Outer Shore Shore Outer Concentratio Concentratio Length Concentratio Length (m) Area (m2) n (mg/L) n (mg/L) (m) n (mg/L) Phosphate 1 0 0 0 0 0 0 2 5 400 1.5 1,400 2.5 287,400 3 0 0 0 0 0 0 4 0.8 400 0.4 1,200 0.3 153,100 Nitrate 1 0 0 0 0 0 0 2 1.4 400 0.6 1,300 0.8 242,400 3 0 0 0 0 0 0 4 1.4 400 0.6 1,300 0.8 242,400

Note: Lake shore values include the two zones coinciding with the constant head boundary (the central area with greatest flow and highest concentration) and the remainder, and indicate the linear distance along which increased nutrient flux is expected. Results of the scenarios that are likely to have the least impacts (Scenarios 1 & 3) predict that phosphate or nitrate is unlikely to reach the lake. An increased volume of freshwater will discharge from the lake bed. Results of scenario that would likely lead to the highest potential impacts (Scenario 2) suggest that phosphate will reach the lake bed along 1,790 m of shoreline (Lake Shore) within 5.5 years and extend 220 m from the shore (Lake Near Shore) with steady state groundwater concentrations reaching up to 2.5 mg/L within 22 years in groundwater discharging from the lake bed (Lake Near Shore).

Table 5 provides a summary of nutrient transport simulation scenarios (i.e. Scenarios 1 to 4) and how the outcomes for each modelled scenario has been interpreted for the purpose of ecological impact assessment.

Table 5 Nutrient transport simulation scenarios

STP Exfiltration induced K R Upgrade & d groundwater constituent Scenario Scenario Case value value Effluent breakthrough from lake bed outcome (PO4) (NO3) Quality H20 Nitrate Phosphate

1 = lowest No upgrade Yes None None Increased potential and existing 2 0.002 freshwater only impacts effluent quality 2 = highest No upgrade Yes Yes Yes Increased potential and existing (High) freshwater, 0.1 0 impacts effluent quality nitrate and high phosphate flux

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STP Exfiltration induced K R Upgrade & d groundwater constituent Scenario Scenario Case value value Effluent breakthrough from lake bed outcome (PO4) (NO3) Quality H20 Nitrate Phosphate

3 = lowest Chemical Yes None None potential Dosing to Increased impacts reduce 2 0.002 freshwater only Phosphate as P to 1.5mg/L 4 Chemical Yes Yes Yes Increased Dosing to (Low) freshwater, reduce 0.1 0 nitrate and low Phosphate as phosphate flux P to 1.5mg/L

4.4 Nutrient flux data It is well recognised in international and local scientific literature that estuarine sediments and the biota that reside within play a major role in recycling nutrients. Sediments accumulate organic matter over time and consequently have a large store of nutrients. Depending on the processes occurring, these nutrients may be locked up in the sediments, converted into biologically unavailable forms, or recycled back into the water column in a form that supports ongoing ecosystem functioning. Microbial breakdown of organic compounds in estuarine sediments is required to mineralise nutrients to a bioavailable form for plants and algae. Mineralised nutrients accumulate in sediment pore-waters and are transported to the overlying water by a number of mechanisms. These include diffusion and a variety of advective mechanisms in which pore-waters and the overlying water are mixed. The term ‘flux’ is used for when materials are transported from the sediments to the overlying water (RiverScience 2005). 4.4.1 Simulated flux rates Table 6 shows the simulated nutrient fluxes for the 4 scenarios in units of grams/day..

Table 6 Modelled Nutrient Fluxes from Groundwater in grams per day (Source: Table 13.10 IGGC (2013)) Total Scenario Lake Shore Lake Near Shore Ocean Shore Ocean Near Shore Lake Phosphate Flux (grams per day) 1 0 0 633 2,744 0 2 2,326 961 770 3,526 3, 287 3 0 0 169 459 0 4 426 90 238 561 516 Nitrate Flux (grams per day) 1 0 0 207 829 0 2 724 200 713 1,154 924 3 0 0 207 829 0 4 724 200 713 1,154 924

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2 Table 7 shows the simulated nutrient fluxes for the 4 scenarios in units of µmol/m /day.

Table 7 Modelled Nutrient Fluxes from Groundwater in µmol/m 2/day (Source: Table 13.11 IGGC (2013)) Lake Shore Lake Shore Lake Near Scenario Lake Shore (all) (central) (outer) Shore Phosphate Flux (µmol P/m2/hr) 1 0 0 0 0 2 2,307 330 769 10 3 0 0 0 0 4 369 88 158 2 Nitrate Flux (µmol N/m2/hr) 1 0 0 0 0 2 646 133 253 3 3 0 0 0 0 4 646 133 253 3

Figure 4 and Figure 5 illustrate the Scenario 2 modelled results for P as phosphate and N as Nitrate plume concentration (mg/L) contours and specific location flux rates (µmol/m2/hr) across the discharge zones. Figure 6 and Figure 7 illustrate the Scenario 3 modelled results for P as phosphate and N as Nitrate plume concentrations contours. Flux rates to Merimbula Lake under this scenario are not shown because the modelling has predicted that there will be no nutrient flux to the lake

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Figure 4 Scenario 2 modelled phosphate flux contour map

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Figure 5 Scenario 2 modelled nitrate flux contour map

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Figure 6 Scenario 3 modelled phosphate flux contour map

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Figure 7 Scenario 3 modelled nitrate flux contour map

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5.0 Impact Assessment

5.1 Preamble This section provides the results of a combination of both: - qualitative assessment of the potential near and far-field ecological impacts - desktop due diligence assessment of matters of ecological significance protected under relevant environmental legislation. This assessment is qualitative and predictive and is based on:  simulated discharges of effluent and modelling of groundwater flow and groundwater nutrient transport  field surveys, algal sampling, literature reviews and interpretations made by Elgin and Associates (Appendix D)  data provided by the EPA and  reference to additional data and reporting from relevant and peer reviewed scientific publications. The steady-state models used by IGGC (2013) were based on average conditions with contaminant transport parameters assumed to be uniform across the model for each scenario. These assumptions are practical requirements of this type of modelling and the results are intended to be indicative only. Actual conditions will vary spatially and temporally and therefore potential impacts will vary spatially and temporally (IGCC 2013). There remains a considerable knowledge gap which limits the ability for any definitive conclusions to be made. Nevertheless, we believe that the groundwater modelling predictions, field surveys, scientific literature reviews and the objective interpretations made are sufficient to provide a useful insight into the likely impacts of the shallow dunal exfiltration option.

5.2 Potential near-field ecological impacts The exfiltration option will deliver freshwater and potentially an additional stream of nutrients into the lake system. This discharge would enter the system through the benthic environment firstly, and then release out into the pelagic or water-column environment through benthic-pelagic coupling mechanisms. Hence any nutrients discharged will connect firstly with micro-phyto benthos and then potentially be accessible to benthic and pelagic macro-algae and the shoreline intertidal mangrove and saltmarsh communities. 5.2.1 Benthic micro and macro algal communities Two of the scenarios suggest that nutrients will be discharged into the lake unless mitigation actions are established. Under these scenarios, areas within any phosphate or especially nitrate plumes may respond to the additional nutrients through the increased growth of benthic microalgae, or micro-phyto benthos (MPB), and macroalgae such as filamentous brown alga. The other two scenarios suggest that only freshwater will enter the lake and hence not result in additional nutrients being discharged, Benthic algal communities in estuaries are dominated by microscopic algae that live in or on sediment or mud surfaces in mangroves, saltmarsh, sand and mudflat environments. Major diatom genera found in the sediments of estuaries along the Australian east coast include Navicula, Nitzschia, Diploneis and Amphora. Other common genera include Achnanthes, Biremis, Planothidium, Hantzschia and Mastologia. (Green et al, in press). Diatoms respond rapidly to increased nutrient concentrations (in the sediments and water column), and are used widely as indicators of environmental change in marine systems and as indicators of eutrophication in coastal waters. Licursi et al (2010) discuss the ecological optima and tolerance ranges of diatoms found on the Argentinean coastline (at a similar latitudes to NSW). A number of genus sampled are found in Lake Merimbula, including: Achnanthes; Amphora; Hantzschia; and Nitzschia. Optima and tolerance ranges for 42 species sampled are summarised in Table 8.

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Table 8 Optima and tolerance ranges of diatoms along Argentinean coastline in mg/L

-3 N-NO3 P-PO4

Optima Low High Optima Low High

Average 0.745 0.329 1.878 0.249 0.135 0.478 Minimum 0.260 0.060 0.520 0.090 0.040 0.120 Maximum 2.472 1.920 6.360 1.010 0.400 2.540

Comparison with the tolerances shown in Table 8, and simulated concentrations for scenario 2 (up to 1.4 N, 5.0 P; lake Shore Central; Table 4) show that for the cases with nutrient discharges the N-NO3 concentrations will be -3 suitable for growth of many species of diatoms likely to be present although the available P-PO4 concentrations may actually exceed measured maximum values for some species, in which case more opportunistic species may flourish. To assess the potential implications of additional nutrient fluxes to benthic micro algal communities, the results of simulated groundwater discharge and nutrient fluxes are considered against natural background benthic fluxes in other estuarine environments. Table 9 provides a summary of nutrient flux data found in literature searches.

Table 9 Summary of nutrient flux data found

Location PO - DIPa DINb NO 4 x Source µmol/m2/hr µmol/m2/hr µmol/m2/hr µmol/m2/hr Australia

Smiths Lake, NSW 0.03 2.54 0.04 Smith & Heggie 2003 Lake Illawarra, NSW 64.00 Qu et al, 2004 Brunswick, NSW 11.00 Eyre and Ferguson 2005 Wattamolla Lagoon, NSW 0.42 Potts et al 2005 Hewitts Lagoon, NSW 4.00 Potts et al 2005 Tramway Lagoon, NSW 4.01 Potts et al 2005 Towradgi Lagoon, NSW 5.49 Potts et al 2005 Fairy Lagoon, NSW 8.10 Potts et al 2005 Lake Wellington (Gippsland Lakes, VIC) 4.60 56.50 Webster et al 2001 Lakes Victoria & King (Gippsland Lakes) (VIC) 5.90 62.50 Webster et al 2001 Stokes Estuary, WA 3.10 -0.30 Murray et al 2008 Swan River Estuary, WA 28.30 Smith et al 2007 Torbay drainage system, WA 111.50 -3.85 Murray et al 2005, 2007 USA

Anacostia River, DC 3.65 Bailey et al., 2003 Mobile Bay, AL 9.25 Cowan et al., 1996 Chester River, MD 25.01 Boynton et al., 2003 Potomac River, MD 20.41 Boynton et al., 2003 Pocomoke River, MD 1.74 Boynton et al., 1999 Patuxent River, MD 26.3 Boynton et al., 2003 Fourleague River, MD -6.67 Teague et al., 1988

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South River, NC 14.7 Fisher et al., 1982 San Francisco Bay, CA 0 Hammond et al., 1985 Chesapeake Bay, USA 24.12 Cowan and Boynton 1996 Chesapeake Bay, USA 2.34 Reay et al 2004 a Dissolved Inorganic Phosphorus (DIP) consist largely of the inorganic orthophosphate (PO4) form of phosphorus. Orthophosphate is the phosphorus form that is directly taken up by algae and plants, and the concentration of this fraction constitutes an index of the amount of phosphorus immediately available for algal and plant growth b Dissolved Inorganic Nitrogen (DIN) = nitrite + nitrate + ammonia Table 7 contains the predicted dissolved N and P fluxes for the simulated scenarios. Table 7 shows that under scenario 2 - the case that has the highest potential impacts yet a low likelihood of occurrence (refer Section 4.2.2), - the flux of nutrients entering into the central lake shore zone are predicted to be up to 2,307 µmol P/m2/hr for dissolved P, and up to 646 µmol N/m2/hr for dissolved N at the specific location of peak discharge. At other locations within the lake near shore zone, the flux of nutrients are predicted to be 10 µmol P/m 2/hr for dissolved P, and 3 µmol N/m2/hr for dissolved N. Comparison with more widespread and background flux rates as reported in Table 9 from estuaries in NSW and Western Australia is as follows:

2  Oxidised nitrogen (N2 + N3) ranging from -3.54 to 0.04 µmol/m /hr are considerably less than predicted Scenario 2 values for the central lake shore zone (646 µmol/m2/hr) and lake near shore zones (3 µmol/m2/hr)

2  DIN (N2 + N3 + NH4 ) ranging from 2.5 to 64.0 µmol/m /hr are comparable with the lake near shore Scenario 2 value for nitrate of 3 µmol N/m2/hr

2  DIP (PO4) ranging from 0.42 to 8.10 µmol/m /hr are considerably less than predicted Scenario 2 values for the central lake shore zone (2,307 µmol/m2/hr) but comparable with the lake near shore Scenario 2 value for phosphate of 10 µmol N/m2/hr Under the worst case scenario 2, it can be argued based on the simulated concentrations and fluxes of particularly dissolved N and P that there will be some level of increased production of micro-algae in the near-field receiving environment around the part of the lake shore where the discharge would occur. This is consistent with other studies, for example numerous studies in Victoria and Western Australia, that have demonstrated the importance of nutrients sourced from sediments in promoting nuisance growth of macrophytes and phytoplankton and/or algal blooms (Fredericks et al. 1999, Roberts et al. 2003, Longmore et al. 2003, Murray et al., 2005a and 2005b, Murray et al., 2008, Smith et al., 2007). It might also be the case that the pore water concentrations and discharge concentrations within a near-field mixing zone will exceed ANZECC (2000) default trigger values for South-east Australia slightly disturbed estuaries (of 0.015 mg/L NOx (N3 + N2)). Under mild enrichment conditions, these changes are commonly not visible unless until very high levels of production occur that can then result in visible microbial mats on the seabed. When conditions favour the formation of a benthic microbial mat of algae, the top layer is usually comprised of cyanobacteria or diatoms. Cyanobacterial species such as Microcoleus chthonoplastes and Oscillatora limosa often dominate the ‘microbial mats’ (Green et al, in press). These mats most commonly occur in regions of low flushing and extended periods of low winds during which vertical mixing in the water-column is reduced. Therefore it is possible, under that some increased microbial production will occur, but not necessarily to the level that would result in visible microbial mats as the majority of the discharge region features stronger flushing. The development of large colonies of filamentous Cyanobacteria such as the common Oscillatoria can also occur in response to higher phosphorus and especially nitrogen levels in the water. With regards to larger and hence more visible macro-algae, Appendix D highlights that opportunistic filamentous taxa that are commonly epiphytic on the blades of seagrasses may respond to the addition of especially increased nitrogen under the high nitrogen-discharge scenario (Scenario 2). It is difficult to predict exactly how much enhanced productivity could occur as it depends on the extent that these dissolved nutrients make their way into the water-column form the sediments. However, as highlighted in Appendix D at times in the nearby Golf Lakes

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can at times be covered up to 50% in algae as a result of the combination of low flushing and anthropogenic nutrient inflows. Appendix D also highlights a lack of hard substrate neat or near the discharge site and hence the biomass of attached broad-leaf macro-algae is constrained by a lack of habitat rather than the availability of nutrients. 5.2.2 Aquatic vegetation Scenarios 1 and 3 indicate that only the flux of freshwater will increase to the lake receiving environment. Therefore under these scenarios substantive impacts to nutrient cycling and vegetation response would not be expected. Under Scenario 2 the highest concentrations of nutrients in groundwater discharge are predicted to occur along the lake shore. This is where saltmarsh and mangrove vegetation is located. Little is reported in relation to the sensitivity of these estuarine communities to groundwater impacts although broad interactions are inferred in general information found through literature searches. Appendix D highlights that a reduction on mean salinity resulting from the freshwater discharge in the saltmarsh community may result in a change in community structure that favours more freshwater tolerant species to proliferate. Similarly, a change in mean salinity in these low flushing communities may also allow mangroves to expand into the saltmarsh community (Rogers and Saintilan 2009). Further out in the near shore zone, seagrasses are found. Simulated nutrient fluxes are considerably lower here than for along the lakeshore. Seagrass is likely to respond to increased nutrients through increased growth, which in turn may result in greater quantities of organic matter and hence carbon recycling in these areas. Whilst in some cases increases in seagrass biomass is seen as advantageous, there are nearby examples of where excessive seagrass growth is considered to be a negative impact, for example at Tuggerah lakes (Dickenson et al, 2006). The significance of the above risks will be largely dependent on the ability of local hydrodynamics to flush concentrations of nutrients entering the water column out to the ocean. Existing literature suggests that the lake on the whole has very good tidal flushing (Appendix D; Webb, McKeown, 1997). Wind blowing across the lake surface also generates surface and sub-surface currents which assist to maintain water quality within the lake by increasing tidal exchange, vertical mixing and oxygenation (Maunsell | AECOM 2008). This is likely to apply to the subject area helping to reduce the potential risk to aquatic ecosystems.

5.3 Potential far-field ecological impacts The additional of new bioavailable nutrients into waterways often only results in detectable near-field impacts, as described above and in Appendix D. However, for larger relative nutrient inflows a potential system-wide impact of the addition of nutrient streams into enclosed and semi-enclosed waterways is an increased eutrophication state of the water body as a result of widespread enhanced biological activity. The lake system represents the receiving environment for existing catchment-derived nutrients, in addition to receiving oceanic nutrients, Roper et al. (2011) reports that 43% of the catchment has been cleared, much of which for agricultural uses and this land use is a source of nutrients into the lake system. Roper et al. (2011) rates the lake system presently as ‘fair’ (Appendix D), with a median chlorophyll a concentration of 2 µg/L. As illustrated in Figure 8, a comparison with other lake systems in NSW, indicates that the standing phytoplankton population, represented through the chlorophyll a biomass, is good. The water quality in the central lake is below ANZECC guidelines and inspection of water quality data indicates high water quality in many parts of the system (Appendix D). Two of the scenarios indicate that only the flux of freshwater will increase to the lake shore. The other two scenarios indicate that there could be some discharge of nutrients into the central lake receiving environment. The CERAT (Coastal Eutrophication Risk Assessment Tool; http://www.ozcoasts.gov.au/nrm_rpt/cerat/index.jsp) reports that the present total nitrogen load into Merimbula Lake is 6,433 kg per year. By comparison, Table 8 indicates that under scenario 2, there might be a discharge of 924 g/day of dissolved nitrogen entering the lake environment. This is equivalent to 0.924 kg/day, or 337 kg per year of dissolved nitrogen. However this figure does not include the organic N contribution. Based on the EPA annual return for 2011/2012, the total N discharge was 3.5 tonnes of TN from a volume discharge of 781 ML. Scaling this up to a projected 2025 total volume of 500 ML remaining for disposal after beneficial reuse gives an estimated total N load of 2.25 tonnes TN discharged per

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year. Assuming 19% (IGGC 2013) of this volume will be directed into the lake, then the total N load into the lake would be 428 kg per year. This means that for the worst case Scenario 2, the discharge of year 2025 estimated disposal volumes to a 400m exfiltration trench located in BVSC land in the dunes east of the airport would potentially contribute an additional 6.7% of TN to Merimbula Lake. From the CERAT model, this increased total nitrogen load would increase the mean chlorophyll a from 2.00 to 2.17 µg/L. Using standard trophic index scales (Carlson 1977), the lake would remain in an oligotrophic or nutrient deficient condition (0-2.6 µg/L chlorophyll a). Furthermore, based on Roper et al. (2011), these values would remain below the monitoring, evaluation and reporting triggers of the NSW Natural Resources Monitoring, Evaluation and Reporting Strategy 2010-2015 (DECCW, 2010).

Figure 8 Comparison of water quality (Chl a µg/L) for NSW coastal lakes

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6.0 Approvals A number of statutory approvals will require consideration in the event that the option of shallow dunal exfiltration was to progress.

6.1 EPBC Act One endangered and several migratory bird species are reported from within or in near proximity to the subject area and are considered to have a high likelihood of utilising a range of habitat features present, such as saltmarsh, mangroves, seagrass, oyster racks, and non-vegetated substratum. Any decrease in availability of habitat in the subject area is unlikely to have a significant impact on nationally important habitat for these species. Merimbula Lake is not identified as a key site for migratory shorebirds (as administered under the East Asian-Australasian Flyway Site Network). However the loss of feeding and roosting habitat; human disturbance at roost and feeding sites; and pollution, are listed threats to many shorebirds protected under the EPBC Act. The EPBC Act is currently under reform, and including SEWPaC consultation for the project is advised.

6.2 TSC Act Saltmarsh is listed as an endangered ecological community under the TSC Act. As inferred in Sections 5.2 and 3.3, the potential impacts on this community are not clear without further detailed investigation (i.e. ground truthing and delineation of extent of saltmarsh within the subject area, and gaining a better understanding of existing sediment characteristics and groundwater quality). As such, consultation with EPA’s Threatened Species Unit is recommended as part of the options development.

6.3 FM Act In accordance with ‘Fish Habitat Protection Plan No.2 Seagrasses’ (DPI, 1997), the discharge of effluent within 50 metres of any seagrass bed will generally not be approved unless special circumstances exist, and effective compensation is provided. In this case the diffuse discharge of effluent in groundwater would arise from effluent discharged approximately 1,000 metres from seagrass beds and as such, consultation with DPI-Fisheries is recommended to understand whether FM Act approval would be required.

6.4 Oyster aquaculture When considering an application for development that, because of its proposed location, may affect a priority oyster aquaculture area or oyster aquaculture outside such an area, the consent authority must: 1) Give the Director-General of the DPI written notice of the development application and take into consideration any written submissions made in response to the notice within 14 days after notice was given. 2) Take into consideration the provisions of the NSW Oyster Industry Sustainable Aquaculture Strategy. 3) Consider any issues that are likely to make the development incompatible with oyster aquaculture and evaluate any measures that the applicant has proposed to address those issues. This assessment has only considered the effects of simulated nutrient concentrations in groundwater discharge, which are not the major parameters that would be of concern to the DPI. Major factors that would require detailed investigation and consideration would include contaminants that may affect human consumption of oysters (in particular heavy metals, faecal coliforms, pathogens and the like). Consultation with the DPI will be required, and potentially the NSW Department of Health may also be required.

6.5 State Environmental Planning Policies Under SEPP 14 – Coastal Wetlands it is likely that the option of shallow dunal exfiltration would be considered designated development. This means the development application will require consultation and concurrence of the Director-General of DoPI and an environmental impact statement and be placed on public exhibition for public comment.

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Under SEPP 71 – Coastal Protection a consent authority must reject development applications that will result in effluent discharge that negatively affects water quality. Consultation with the DoPI should be facilitated if this option is to proceed further.

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7.0 References AECOM | Maunsell, 2008, ‘Merimbula Lake Artificial Reef Project,’ Statement of Environmental Effects prepared for NSW Department of Primary Industries, Fisheries, April 2008 ANCA 1996, ‘A Directory of Important Wetlands in Australia,’ 2nd Edition, Australian Nature Conservation Agency, Canberra Bailey, E. K. M., R. M. Stankelis, P. W. Smail, S. Greene, F. M. Rohland, and Boynton, W.R. 2003. Dissolved Oxygen and Nutrient Flux Estimation from Sediments in the Anacostia River. University of Maryland Center for Environmental Science, Chesapeake Bay Laboratory. Solomons, MD. Carlson, R.E., 1977. A trophic state index for lakes. Limnology and Oceanography Vol. 22, pp 361-368. Creese, R.G., Glasby, T.M., West, G., and Gallen, C. 2009, ‘Mapping the habitats of NSW estuaries,’ Industry & Investment NSW Fisheries Final Report Series 113. Port Stephens, NSW, Australia. ISSN 1837-2112 pp 95 Day, J.H. and Hutchings P.A.. 1984. An annotated list of the fauna and flora of Merimbula and Pambula Lake N.S.W. Australian Zoologist, vol 21. No. 2–3, pp. 263–289. Department of Environment and Climate Change (DECC) 2007, ‘Threatened Species Assessment Guidelines: The Assessment of Significance,’ DECC, Sydney. Department of Environment, Climate Change and Water (DECCW) 2010, NSW Natural Resources Monitoring, Evaluation and Reporting Strategy 2010-2015. Department of Primary Industries 2006, ‘NSW Oyster Industry – Sustainable Aquaculture Strategy,’, NSW, Australia. Dickenson, T.G., Roberts, D.E., Geary, M., McPherson, R., Dye, A., Muston, R., 2006 ‘Tuggerah Lakes Estuary Management Plan’. Prepared for Wyong Shire Council and Department of Natural Resources. BIO-ANALYSIS Pty Ltd: Marine, Estuarine and Freshwater Ecology, Narara. Eyre, B. D. and Ferguson, A. J. P. 2005. Benthic metabolism and nitrogen cycling in a sub-tropical east Australian estuary (Brunswick) - temporal variability and controlling factors. Limnology and Oceanography 50, pp. 81-96. Fredericks, D, Heggie, D, Longmore, A, Palmer, D, Smith, C & Skyring, G 1999 ‘Nutrient recycling and benthic activity in a shallow coastal lagoon in Western Australia.’ Research News. No. 31. AGSO, Canberra. IGCC 2013, Disposal of Effluent from Merimbula Sewage Treatment Plant by Dunal Exfiltration – Investigation and Assessment of Impacts on Groundwater Levels and Water Quality of Merimbula Lake and Bay. IGGC, pp 162 Green, J., Catterall, C., Sonneman, J., in press, ‘Micro-algae’ in ‘Estuary Plants south east Australia: what’s happening?’ Sainty and Associates Pty Ltd, Potts Point NSW, pp 36-43 Licursi, M., Gomez, N., and Donadelli, J., 2010 ‘Ecological optima and tolerances of coastal benthic diatoms in the freshwater-mixohaline zone of the Rio de la Plata estuary’ Marine Ecology Progress Series Vol. 418, pp 105-117 Longmore, A.R., Roberts, S. and Light, B. 2003, ‘Gippsland Lakes Future Directions and Actions Plan Task 3.7: Assessment of the importance of sediment-bound nutrients.’ Marine and Freshwater Systems Internal Report No. 60. Marine and Freshwater Systems: Queenscliff. Massel, S. R.; Furukawa, K., and Brinkman R. M. 1999 ’Surface wave propagation in mangrove forests’ Fluid Dynamics Research, vol. 24, no. 4, pp.219-249 Mazda, Y.; Kobashi, D. and Okada, S., 2005, ‘Tidal-Scale Hydrodynamics within Mangrove Swamps’ Wetlands Ecology and Management vol. 13, no. 6, pp. 647-655 Mazda, Yoshihiro et al., 1997. ‘Drag force due to vegetation in mangrove swamps’ Mangroves and Salt Marshes Merimbula Big Game and Lakes Angling Club, 2012, ‘Weekly Fishing Report’ October 2009 to October 2011 accessed 06.06.2012, available at: http://www.fishmerimbula.com.au/index.php/events/fishing-report Murray, E. J., Haese, R. R., Smith, C. S. and Heggie, D. T. 2005a, ‘Nutrient Cycling in St Georges Basin, South Coast NSW’ Report on Field Survey November 2003. Geoscience Australia, Record 2005/22 pp. 79

6 March 2013 AECOM Merimbula Effluent Management Options Investigation 33 Ecological Assessment of the Potential Impacts on Merimbula Lake from Shallow Dunal Exfiltration of Effluent

Murray, E.J., Smith, C.S., Smith, J., Haese, R.R., and Heggie, D.T. 2005b, ‘Nutrient Release from Sediments of the Torbay Drainage System, South-Western Australia,’ Geoscience Australia Record 2005/14 pp. 76 Murray, E., Haese, R., Grosjean, E., Macphail, M., and Hancock, G. 2008, ‘Historic environmental changes and present-day nutrient release from sediments in Stokes Inlet and Wellstead Estuary, south-western Australia,’ Geoscience Australia Record 2008/22, Commonwealth Government, Canberra, pp.52

OzCoasts 2012. www.ozcoasts.gov.au Potts, J., Blakey, C., Watson, R. 2005. Nutrient fluxes in 5 lagoons along the Illawarra coast. Report of Wollongong City Council, Department of Environment and Conservation, Sydney. Qu, w., Morrison, R.J., and West R.J. 2004. Nitrogen cycling processes in Lake Illawarra, an intermittently closed/open estuary in south-east Australia. Wetlands (Australia), Vol 21, No 2, pp 288-303 Reay W.G., 2004, ‘Septic Tank Impacts on Ground Water Quality and Nearshore Sediment Nutrient Flux,’ Ground Water - Oceans Issue, 2004, vol. 42, no. 7, pg 1079–1089 Roberts, S., Hart, B.T., Holland, D., Longmore, A., Nicholson, G. and Light, B. 2003, ‘Algal blooms in the Gippsland Lakes: Assessment of the importance of sediment-bound nutrients,’ Technical Report for Coasts and Clean Seas project V00-32-M, Water Studies Centre, Monash University, Clayton. Rogers, K and Saintilan N., 2009 ‘Predicting the Response of Coastal Wetlands of Southeastern Australia to Sea- level Rise’ 18th NSW Coastal Conference proceedings Roper, T., Creese, B., Scanes, P., Stephens, K., Williams, R., Dela-Cruz, J., Coade, G. and Coates, B. 2011. Assessing the condition of estuaries and coastal lake ecosystems in NSW. Office of Environment and Heritage, Sydney. pp.270. Roy, P.S., Williams, R.J., Jones, A.R., Yassini, I., Gibbs, P.J., Coates, B., West, R.J., Scanes, P.R., Hudson, J.P. and Nichol, S. 2001, Structure and Function of South-east Australian Estuaries. Estuarine, Coastal and Shelf Science Vol. 53, pp. 351-384 Smith, C.S., and Heggie, D.T., 2003. Benthic nutrient fluxes in Smiths Lake, NSW. Geoscience Australia Record 2003/16 pp 27 Smith, C.S., Murray, E.J., Hepplewhite, C. and Haese, R.R. 2007, ‘Sediment water interactions in the Swan River estuary: Findings and management implications from benthic nutrient surveys, 2000-2006,’ Geoscience Australia Record 2007/13 pp 75 Webster, I., Parslow, J., Grayson, R., Molloy, R., Andrewartha, J., Sakov, P., Tan, K., Walker, J., and Wallace, B. 2001. Gippsland Lakes Environmental Study - Assessing options for improving water quality and ecological function. Final report submitted to Gippsland Coastal Board.

6 March 2013 AECOM Merimbula Effluent Management Options Investigation Ecological Assessment of the Potential Impacts on Merimbula Lake from Shallow Dunal Exfiltration of Effluent

Appendix A

IGCC figures

6 March 2013 AECOM Merimbula Effluent Management Options Investigation A-1 Ecological Assessment of the Potential Impacts on Merimbula Lake from Shallow Dunal Exfiltration of Effluent

Appendix A IGCC figures

IGGC Figures are provided within Appendix D – Supplementary Report (Elgin Associates, 2013)

6 March 2013 AECOM Merimbula Effluent Management Options Investigation Ecological Assessment of the Potential Impacts on Merimbula Lake from Shallow Dunal Exfiltration of Effluent

Appendix B

Government database search results

6 March 2013

EPBC Act Protected Matters Report

This report provides general guidance on matters of national environmental significance and other matters protected by the EPBC Act in the area you have selected.

Information on the coverage of this report and qualifications on data supporting this report are contained in the caveat at the end of the report.

Information about the EPBC Act including significance guidelines, forms and application process details can be found at http://www.environment.gov.au/epbc/assessmentsapprovals/index.html

Report created: 09/06/12 16:34:59

Summary Details Matters of NES Other Matters Protected by the EPBC Act Extra Information Caveat Acknowledgements

This map may contain data which are ©Commonwealth of Australia (Geoscience Australia), ©PSMA 2010

Coordinates Buffer: 10.0Km

Summary

Matters of National Environment Significance

This part of the report summarises the matters of national environmental significance that may occur in, or may relate to, the area you nominated. Further information is available in the detail part of the report, which can be accessed by scrolling or following the links below. If you are proposing to undertake an activity that may have a significant impact on one or more matters of national environmental significance then you should consider the Administrative Guidelines on Significance - see http://www.environment.gov.au/epbc/assessmentsapprovals/guidelines/index.html

World Heritage Properties: None National Heritage Places: None Wetlands of International None Great Barrier Reef Marine Park: None Commonwealth Marine Areas: 1 Threatened Ecological Communities: 1 Threatened Species: 53 Migratory Species: 47

Other Matters Protected by the EPBC Act

This part of the report summarises other matters protected under the Act that may relate to the area you nominated. Approval may be required for a proposed activity that significantly affects the environment on Commonwealth land, when the action is outside the Commonwealth land, or the environment anywhere when the action is taken on Commonwealth land. Approval may also be required for the Commonwealth or Commonwealth agencies proposing to take an action that is likely to have a significant impact on the environment anywhere.

The EPBC Act protects the environment on Commonwealth land, the environment from the actions taken on Commonwealth land, and the environment from actions taken by Commonwealth agencies. As heritage values of a place are part of the 'environment', these aspects of the EPBC Act protect the Commonwealth Heritage values of a Commonwealth Heritage place and the heritage values of a place on the Register of the National Estate. Information on the new heritage laws can be found at http://www.environment.gov.au/heritage/index.html

This part of the report summarises other matters protected under the Act that may relate to the area you nominated. Approval may be required for a proposed activity that significantly affects the environment on Commonwealth land, when the action is outside the Commonwealth land, or the environment anywhere when the action is taken on Commonwealth land. Approval may also be required for the Commonwealth or Commonwealth agencies proposing to take an action that is likely to have a significant impact on the environment anywhere.

A permit may be required for activities in or on a Commonwealth area that may affect a member of a listed threatened species or ecological community, a member of a listed migratory species, whales and other cetaceans, or a member of a listed marine species. Information on EPBC Act permit requirements and application forms can be found at http://www.environment.gov.

Commonwealth Lands: 1 Commonwealth Heritage Places: None Listed Marine Species: 69 Whales and Other Cetaceans: 12 Critical Habitats: None Commonwealth Reserves: None

Extra Information

This part of the report provides information that may also be relevant to the area you have

Place on the RNE: 8 State and Territory Reserves: 4 Regional Forest Agreements: 1 Invasive Species: 13 Nationally Important Wetlands: 3

Details

Matters of National Environmental Significance Commonwealth Marine Areas [ Resource Information ] Approval may be required for a proposed activity that is likely to have a significant impact on the environment in a Commonwealth Marine Area, when the action is outside the Commonwealth Marine Area, or the environment anywhere when the action is taken within the Commonwealth Marine Area. Generally the Commonwealth Marine Area stretches from three nautical miles to two hundred Name EEZ and Territorial Sea

Threatened Ecological Communities [ Resource Information ]

For threatened ecological communities where the distribution is well known, maps are derived from recovery plans, State vegetation maps, remote sensing imagery and other sources. Where threatened ecological community distributions are less well known, existing vegetation maps and point location data are used to produce indicative distribution maps. Name Status Type of Presence Littoral Rainforest and Coastal Vine Thickets of Critically Endangered Community likely to Eastern Australia occur within area Threatened Species [ Resource Information ] Name Status Type of Presence BIRDS Anthochaera phrygia Regent Honeyeater [82338] Endangered Species or species habitat may occur within area Botaurus poiciloptilus Australasian Bittern [1001] Endangered Species or species habitat known to occur within area Dasyornis brachypterus Eastern Bristlebird [533] Endangered Species or species habitat known to occur within area Diomedea epomophora epomophora Southern Royal Albatross [25996] Vulnerable Species or species habitat may occur within area Diomedea epomophora sanfordi Northern Royal Albatross [82331] Endangered Species or species habitat may occur within area Diomedea exulans amsterdamensis Amsterdam Albatross [82330] Endangered Species or species habitat may occur within area Diomedea exulans antipodensis Antipodean Albatross [82269] Vulnerable Species or species habitat may occur within area Diomedea exulans exulans Tristan Albatross [82337] Endangered Foraging, feeding or related behaviour may occur within area Diomedea exulans gibsoni Gibson's Albatross [82271] Vulnerable Species or species habitat may occur within area Diomedea exulans (sensu lato) Wandering Albatross [1073] Vulnerable Species or species habitat may occur within area Fregetta grallaria grallaria White-bellied Storm-Petrel (Tasman Sea), White- Vulnerable Species or species bellied Storm-Petrel (Australasian) [64438] habitat likely to occur within area Halobaena caerulea Blue Petrel [1059] Vulnerable Species or species habitat may occur within area Lathamus discolor Swift Parrot [744] Endangered Species or species habitat likely to occur within area Macronectes giganteus Southern Giant-Petrel [1060] Endangered Species or species habitat may occur within area Macronectes halli Northern Giant-Petrel [1061] Vulnerable Species or species habitat may occur within area Neophema chrysogaster Orange-bellied Parrot [747] Critically Endangered Species or species

Name Status Type of Presence habitat may occur within area Rostratula australis Australian Painted Snipe [77037] Vulnerable Species or species habitat may occur within area Sternula nereis nereis Fairy Tern (Australian) [82950] Vulnerable Species or species habitat known to occur within area Thalassarche bulleri Buller's Albatross [64460] Vulnerable Species or species habitat may occur within area Thalassarche cauta cauta Shy Albatross, Tasmanian Shy Albatross [82345] Vulnerable Species or species habitat may occur within area Thalassarche cauta salvini Salvin's Albatross [82343] Vulnerable Species or species habitat may occur within area Thalassarche cauta steadi White-capped Albatross [82344] Vulnerable Species or species habitat may occur within area Thalassarche chrysostoma Grey-headed Albatross [66491] Endangered Species or species habitat may occur within area Thalassarche melanophris Black-browed Albatross [66472] Vulnerable Species or species habitat may occur within area Thalassarche melanophris impavida Campbell Albatross [82449] Vulnerable Species or species habitat may occur within area FISH Epinephelus daemelii Black Rockcod, Black Cod, Saddled Rockcod Vulnerable Species or species [68449] habitat may occur within area Prototroctes maraena Australian Grayling [26179] Vulnerable Species or species habitat likely to occur within area FROGS Heleioporus australiacus Giant Burrowing Frog [1973] Vulnerable Species or species habitat likely to occur within area Litoria aurea Green and Golden Bell Frog [1870] Vulnerable Species or species habitat likely to occur within area Litoria littlejohni Littlejohn's Tree Frog, Heath Frog [64733] Vulnerable Species or species habitat may occur within area Mixophyes balbus Stuttering Frog, Southern Barred Frog (in Victoria) Vulnerable Species or species [1942] habitat likely to occur within area MAMMALS Balaenoptera musculus Blue Whale [36] Endangered Species or species habitat likely to occur within area Dasyurus maculatus maculatus (SE mainland population) Spot-tailed Quoll, Spotted-tail Quoll, Tiger Quoll Endangered Species or species (southeastern mainland population) [75184] habitat may occur within area

Name Status Type of Presence Eubalaena australis Southern Right Whale [40] Endangered Species or species habitat known to occur within area Isoodon obesulus obesulus Southern Brown Bandicoot (Eastern) [68050] Endangered Species or species habitat likely to occur within area Megaptera novaeangliae Humpback Whale [38] Vulnerable Congregation or aggregation known to occur within area Petrogale penicillata Brush-tailed Rock-wallaby [225] Vulnerable Species or species habitat likely to occur within area Phascolarctos cinereus (combined populations of Qld, NSW and the ACT) Koala (combined populations of Queensland, New Vulnerable Species or species South Wales and the Australian Capital Territory) habitat known to occur [85104] within area Potorous longipes Long-footed Potoroo [217] Endangered Species or species habitat likely to occur within area Potorous tridactylus tridactylus Long-nosed Potoroo (SE mainland) [66645] Vulnerable Species or species habitat may occur within area Pseudomys fumeus Konoom, Smoky Mouse [88] Endangered Species or species habitat may occur within area Pseudomys novaehollandiae New Holland Mouse [96] Vulnerable Species or species habitat likely to occur within area Pteropus poliocephalus Grey-headed Flying-fox [186] Vulnerable Roosting known to occur within area PLANTS Correa baeuerlenii Chef's Cap [17007] Vulnerable Species or species habitat likely to occur within area Cryptostylis hunteriana Leafless Tongue-orchid [19533] Vulnerable Species or species habitat may occur within area Pomaderris parrisiae Parris' Pomaderris [22119] Vulnerable Species or species habitat likely to occur within area REPTILES Caretta caretta Loggerhead Turtle [1763] Endangered Species or species habitat likely to occur within area Chelonia mydas Green Turtle [1765] Vulnerable Species or species habitat likely to occur within area Dermochelys coriacea Leatherback Turtle, Leathery Turtle, Luth [1768] Endangered Species or species habitat likely to occur within area Eretmochelys imbricata Hawksbill Turtle [1766] Vulnerable Species or species habitat likely to occur within area SHARKS Carcharias taurus (east coast population) Grey Nurse Shark (east coast population) [68751] Critically Endangered Species or species habitat may occur within

Name Status Type of Presence area Carcharodon carcharias Great White Shark [64470] Vulnerable Species or species habitat may occur within area Rhincodon typus Whale Shark [66680] Vulnerable Species or species habitat may occur within area Migratory Species [ Resource Information ] * Species is listed under a different scientific name on the EPBC Act - Threatened Species list. Name Threatened Type of Presence Migratory Marine Birds Apus pacificus Fork-tailed Swift [678] Species or species habitat may occur within area Ardea alba Great Egret, White Egret [59541] Species or species habitat may occur within area Ardea ibis Cattle Egret [59542] Species or species habitat may occur within area Diomedea amsterdamensis Amsterdam Albatross [64405] Endangered* Species or species habitat may occur within area Diomedea antipodensis Antipodean Albatross [64458] Vulnerable* Species or species habitat may occur within area Diomedea dabbenena Tristan Albatross [66471] Endangered* Foraging, feeding or related behaviour may occur within area Diomedea epomophora (sensu stricto) Southern Royal Albatross [1072] Vulnerable* Species or species habitat may occur within area Diomedea exulans (sensu lato) Wandering Albatross [1073] Vulnerable Species or species habitat may occur within area Diomedea gibsoni Gibson's Albatross [64466] Vulnerable* Species or species habitat may occur within area Diomedea sanfordi Northern Royal Albatross [64456] Endangered* Species or species habitat may occur within area Macronectes giganteus Southern Giant-Petrel [1060] Endangered Species or species habitat may occur within area Macronectes halli Northern Giant-Petrel [1061] Vulnerable Species or species habitat may occur within area Sterna albifrons Little Tern [813] Species or species habitat may occur within area Thalassarche bulleri Buller's Albatross [64460] Vulnerable Species or species habitat may occur within area Thalassarche cauta (sensu stricto) Shy Albatross, Tasmanian Shy Albatross [64697] Vulnerable* Species or species habitat may occur within

Name Threatened Type of Presence area Thalassarche chrysostoma Grey-headed Albatross [66491] Endangered Species or species habitat may occur within area Thalassarche impavida Campbell Albatross [64459] Vulnerable* Species or species habitat may occur within area Thalassarche melanophris Black-browed Albatross [66472] Vulnerable Species or species habitat may occur within area Thalassarche salvini Salvin's Albatross [64463] Vulnerable* Species or species habitat may occur within area Thalassarche steadi White-capped Albatross [64462] Vulnerable* Species or species habitat may occur within area Migratory Marine Species Balaenoptera edeni Bryde's Whale [35] Species or species habitat may occur within area Balaenoptera musculus Blue Whale [36] Endangered Species or species habitat likely to occur within area Caperea marginata Pygmy Right Whale [39] Species or species habitat may occur within area Carcharodon carcharias Great White Shark [64470] Vulnerable Species or species habitat may occur within area Caretta caretta Loggerhead Turtle [1763] Endangered Species or species habitat likely to occur within area Chelonia mydas Green Turtle [1765] Vulnerable Species or species habitat likely to occur within area Dermochelys coriacea Leatherback Turtle, Leathery Turtle, Luth [1768] Endangered Species or species habitat likely to occur within area Eretmochelys imbricata Hawksbill Turtle [1766] Vulnerable Species or species habitat likely to occur within area Eubalaena australis Southern Right Whale [40] Endangered Species or species habitat known to occur within area Lagenorhynchus obscurus Dusky Dolphin [43] Species or species habitat may occur within area Lamna nasus Porbeagle, Mackerel Shark [83288] Species or species habitat likely to occur within area Megaptera novaeangliae Humpback Whale [38] Vulnerable Congregation or aggregation known to occur within area Orcinus orca Killer Whale, Orca [46] Species or species habitat may occur within

Name Threatened Type of Presence area Rhincodon typus Whale Shark [66680] Vulnerable Species or species habitat may occur within area Migratory Terrestrial Species Haliaeetus leucogaster White-bellied Sea-Eagle [943] Species or species habitat likely to occur within area Hirundapus caudacutus White-throated Needletail [682] Species or species habitat may occur within area Merops ornatus Rainbow Bee-eater [670] Species or species habitat may occur within area Monarcha melanopsis Black-faced Monarch [609] Species or species habitat known to occur within area Myiagra cyanoleuca Satin Flycatcher [612] Breeding likely to occur within area Neophema chrysogaster Orange-bellied Parrot [747] Critically Endangered Species or species habitat may occur within area Rhipidura rufifrons Rufous Fantail [592] Breeding may occur within area Xanthomyza phrygia Regent Honeyeater [430] Endangered* Species or species habitat may occur within area Migratory Wetlands Species Ardea alba Great Egret, White Egret [59541] Species or species habitat may occur within area Ardea ibis Cattle Egret [59542] Species or species habitat may occur within area Gallinago hardwickii Latham's Snipe, Japanese Snipe [863] Foraging, feeding or related behaviour may occur within area Numenius minutus Little Curlew, Little Whimbrel [848] Foraging, feeding or related behaviour likely to occur within area Rostratula benghalensis (sensu lato) Painted Snipe [889] Vulnerable* Species or species habitat may occur within area

Other Matters Protected by the EPBC Act Commonwealth Lands [ Resource Information ] The Commonwealth area listed below may indicate the presence of Commonwealth land in this vicinity. Due to the unreliability of the data source, all proposals should be checked as to whether it impacts on a Commonwealth area, before making a definitive decision. Contact the State or Territory government land department for further information. Name Commonwealth Land - Australian Telecommunications Commission

Listed Marine Species [ Resource Information ] * Species is listed under a different scientific name on the EPBC Act - Threatened Species list. Name Threatened Type of Presence Birds Apus pacificus Fork-tailed Swift [678] Species or species habitat may occur within area Ardea alba Great Egret, White Egret [59541] Species or species habitat may occur within area Ardea ibis Cattle Egret [59542] Species or species habitat may occur within area Catharacta skua Great Skua [59472] Species or species habitat may occur within area Diomedea amsterdamensis Amsterdam Albatross [64405] Endangered* Species or species habitat may occur within area Diomedea antipodensis Antipodean Albatross [64458] Vulnerable* Species or species habitat may occur within area Diomedea dabbenena Tristan Albatross [66471] Endangered* Foraging, feeding or related behaviour may occur within area Diomedea epomophora (sensu stricto) Southern Royal Albatross [1072] Vulnerable* Species or species habitat may occur within area Diomedea exulans (sensu lato) Wandering Albatross [1073] Vulnerable Species or species habitat may occur within area Diomedea gibsoni Gibson's Albatross [64466] Vulnerable* Species or species habitat may occur within area Diomedea sanfordi Northern Royal Albatross [64456] Endangered* Species or species habitat may occur within area Gallinago hardwickii Latham's Snipe, Japanese Snipe [863] Foraging, feeding or related behaviour may occur within area Gallinago megala Swinhoe's Snipe [864] Foraging, feeding or related behaviour likely to occur within area Gallinago stenura Pin-tailed Snipe [841] Foraging, feeding or related behaviour likely to occur within area Haliaeetus leucogaster White-bellied Sea-Eagle [943] Species or species habitat likely to occur within area Halobaena caerulea Blue Petrel [1059] Vulnerable Species or species habitat may occur within area Hirundapus caudacutus White-throated Needletail [682] Species or species habitat may occur within area

Name Threatened Type of Presence Lathamus discolor Swift Parrot [744] Endangered Species or species habitat likely to occur within area Macronectes giganteus Southern Giant-Petrel [1060] Endangered Species or species habitat may occur within area Macronectes halli Northern Giant-Petrel [1061] Vulnerable Species or species habitat may occur within area Merops ornatus Rainbow Bee-eater [670] Species or species habitat may occur within area Monarcha melanopsis Black-faced Monarch [609] Species or species habitat known to occur within area Myiagra cyanoleuca Satin Flycatcher [612] Breeding likely to occur within area Neophema chrysogaster Orange-bellied Parrot [747] Critically Endangered Species or species habitat may occur within area Numenius minutus Little Curlew, Little Whimbrel [848] Foraging, feeding or related behaviour likely to occur within area Rhipidura rufifrons Rufous Fantail [592] Breeding may occur within area Rostratula benghalensis (sensu lato) Painted Snipe [889] Vulnerable* Species or species habitat may occur within area Sterna albifrons Little Tern [813] Species or species habitat may occur within area Thalassarche bulleri Buller's Albatross [64460] Vulnerable Species or species habitat may occur within area Thalassarche cauta (sensu stricto) Shy Albatross, Tasmanian Shy Albatross [64697] Vulnerable* Species or species habitat may occur within area Thalassarche chrysostoma Grey-headed Albatross [66491] Endangered Species or species habitat may occur within area Thalassarche impavida Campbell Albatross [64459] Vulnerable* Species or species habitat may occur within area Thalassarche melanophris Black-browed Albatross [66472] Vulnerable Species or species habitat may occur within area Thalassarche salvini Salvin's Albatross [64463] Vulnerable* Species or species habitat may occur within area Thalassarche steadi White-capped Albatross [64462] Vulnerable* Species or species habitat may occur within area Thinornis rubricollis rubricollis Hooded Plover (eastern) [66726] Species or species habitat likely to occur

Name Threatened Type of Presence within area Fish Heraldia nocturna Upside-down Pipefish, Eastern Upside-down Species or species Pipefish, Eastern Upside-down Pipefish [66227] habitat may occur within area Hippocampus abdominalis Bigbelly Seahorse, Eastern Potbelly Seahorse, New Species or species Zealand Potbelly Seahorse [66233] habitat may occur within area Hippocampus breviceps Short-head Seahorse, Short-snouted Seahorse Species or species [66235] habitat may occur within area Hippocampus minotaur Bullneck Seahorse [66705] Species or species habitat may occur within area Hippocampus whitei White's Seahorse, Crowned Seahorse, Sydney Species or species Seahorse [66240] habitat may occur within area Histiogamphelus briggsii Crested Pipefish, Briggs' Crested Pipefish, Briggs' Species or species Pipefish [66242] habitat may occur within area Histiogamphelus cristatus Rhino Pipefish, Macleay's Crested Pipefish, Ring- Species or species back Pipefish [66243] habitat may occur within area Hypselognathus rostratus Knifesnout Pipefish, Knife-snouted Pipefish Species or species [66245] habitat may occur within area Kaupus costatus Deepbody Pipefish, Deep-bodied Pipefish [66246] Species or species habitat may occur within area Kimblaeus bassensis Trawl Pipefish, Bass Strait Pipefish [66247] Species or species habitat may occur within area Leptoichthys fistularius Brushtail Pipefish [66248] Species or species habitat may occur within area Lissocampus runa Javelin Pipefish [66251] Species or species habitat may occur within area Maroubra perserrata Sawtooth Pipefish [66252] Species or species habitat may occur within area Mitotichthys semistriatus Halfbanded Pipefish [66261] Species or species habitat may occur within area Mitotichthys tuckeri Tucker's Pipefish [66262] Species or species habitat may occur within area Notiocampus ruber Red Pipefish [66265] Species or species habitat may occur within area Phyllopteryx taeniolatus Common Seadragon, Weedy Seadragon [66268] Species or species habitat may occur within area Solegnathus robustus Robust Pipehorse, Robust Spiny Pipehorse Species or species [66274] habitat may occur within

Name Threatened Type of Presence area Solegnathus spinosissimus Spiny Pipehorse, Australian Spiny Pipehorse Species or species [66275] habitat may occur within area Stigmatopora argus Spotted Pipefish, Gulf Pipefish [66276] Species or species habitat may occur within area Stigmatopora nigra Widebody Pipefish, Wide-bodied Pipefish, Black Species or species Pipefish [66277] habitat may occur within area Stipecampus cristatus Ringback Pipefish, Ring-backed Pipefish [66278] Species or species habitat may occur within area Syngnathoides biaculeatus Double-end Pipehorse, Double-ended Pipehorse, Species or species Alligator Pipefish [66279] habitat may occur within area Urocampus carinirostris Hairy Pipefish [66282] Species or species habitat may occur within area Vanacampus margaritifer Mother-of-pearl Pipefish [66283] Species or species habitat may occur within area Vanacampus phillipi Port Phillip Pipefish [66284] Species or species habitat may occur within area Vanacampus poecilolaemus Longsnout Pipefish, Australian Long-snout Species or species Pipefish, Long-snouted Pipefish [66285] habitat may occur within area Mammals Arctocephalus forsteri New Zealand Fur-seal [20] Species or species habitat may occur within area Arctocephalus pusillus Australian Fur-seal, Australo-African Fur-seal Species or species [21] habitat may occur within area Reptiles Caretta caretta Loggerhead Turtle [1763] Endangered Species or species habitat likely to occur within area Chelonia mydas Green Turtle [1765] Vulnerable Species or species habitat likely to occur within area Dermochelys coriacea Leatherback Turtle, Leathery Turtle, Luth [1768] Endangered Species or species habitat likely to occur within area Eretmochelys imbricata Hawksbill Turtle [1766] Vulnerable Species or species habitat likely to occur within area Whales and other Cetaceans [ Resource Information ] Name Status Type of Presence Mammals Balaenoptera acutorostrata Minke Whale [33] Species or species habitat may occur within area

Name Status Type of Presence Balaenoptera edeni Bryde's Whale [35] Species or species habitat may occur within area Balaenoptera musculus Blue Whale [36] Endangered Species or species habitat likely to occur within area Caperea marginata Pygmy Right Whale [39] Species or species habitat may occur within area Delphinus delphis Common Dophin, Short-beaked Common Species or species Dolphin [60] habitat may occur within area Eubalaena australis Southern Right Whale [40] Endangered Species or species habitat known to occur within area Grampus griseus Risso's Dolphin, Grampus [64] Species or species habitat may occur within area Lagenorhynchus obscurus Dusky Dolphin [43] Species or species habitat may occur within area Megaptera novaeangliae Humpback Whale [38] Vulnerable Congregation or aggregation known to occur within area Orcinus orca Killer Whale, Orca [46] Species or species habitat may occur within area Tursiops aduncus Indian Ocean Bottlenose Dolphin, Spotted Species or species Bottlenose Dolphin [68418] habitat likely to occur within area Tursiops truncatus s. str. Bottlenose Dolphin [68417] Species or species habitat may occur within area

Extra Information Places on the RNE [ Resource Information ] Note that not all Indigenous sites may be listed. Name State Status Natural Yowaka Reserve Proposal NSW Indicative Place Bournda National Park NSW Interim List Ben Boyd National Park NSW Registered Bournda Nature Reserve NSW Registered Indigenous Pambula Beach Midden Complex NSW Indicative Place Historic Courthouse / Police Station and Cell Block (former) NSW Registered Courunga House, Grounds and Trees NSW Registered School and Residence (former) NSW Registered

State and Territory Reserves [ Resource Information ] Name State Ben Boyd NSW Bournda NSW

Name State Bournda NSW South East Forest NSW

Regional Forest Agreements [ Resource Information ] Note that all areas with completed RFAs have been included. Name State Eden RFA New South Wales

Invasive Species [ Resource Information ] Weeds reported here are the 20 species of national significance (WoNS), along with other introduced plants that are considered by the States and Territories to pose a particularly significant threat to biodiversity. The following feral animals are reported: Goat, Red Fox, Cat, Rabbit, Pig, Water Buffalo and Cane Toad. Maps from Landscape Health Project, National Land and Water Resouces Audit, Name Status Type of Presence Mammals Felis catus Cat, House Cat, Domestic Cat [19] Species or species habitat likely to occur within area Oryctolagus cuniculus Rabbit, European Rabbit [128] Species or species habitat likely to occur within area Vulpes vulpes Red Fox, Fox [18] Species or species habitat likely to occur within area Plants Asparagus asparagoides Bridal Creeper, Bridal Veil Creeper, Smilax, Species or species Florist's Smilax, Smilax Asparagus [22473] habitat likely to occur within area Lantana camara Lantana, Common Lantana, Kamara Lantana, Species or species Large-leaf Lantana, Pink Flowered Lantana, Red habitat likely to occur Flowered Lantana, Red-Flowered Sage, White within area Sage, Wild Sage [10892] Lycium ferocissimum African Boxthorn, Boxthorn [19235] Species or species habitat may occur within area Nassella neesiana Chilean Needle grass [67699] Species or species habitat likely to occur within area Nassella trichotoma Serrated Tussock, Yass River Tussock, Yass Species or species Tussock, Nassella Tussock (NZ) [18884] habitat likely to occur within area Pinus radiata Radiata Pine Monterey Pine, Insignis Pine, Wilding Species or species Pine [20780] habitat may occur within area Rubus fruticosus aggregate Blackberry, European Blackberry [68406] Species or species habitat likely to occur within area Salix spp. except S.babylonica, S.x calodendron & S.x reichardtii Willows except Weeping Willow, Pussy Willow and Species or species Sterile Pussy Willow [68497] habitat likely to occur within area Salvinia molesta Salvinia, Giant Salvinia, Aquarium Watermoss, Species or species Kariba Weed [13665] habitat likely to occur within area Ulex europaeus Gorse, Furze [7693] Species or species habitat likely to occur within area Nationally Important Wetlands [ Resource Information ]

Name State Bondi Lake NSW Merimbula Lake NSW Pambula Estuarine Wetlands NSW

Coordinates -36.89331 149.91492

Caveat The information presented in this report has been provided by a range of data sources as acknowledged at the end of the report. This report is designed to assist in identifying the locations of places which may be relevant in determining obligations under the Environment Protection and Biodiversity Conservation Act 1999. It holds mapped locations of World Heritage and Register of National Estate properties, Wetlands of International Importance, Commonwealth and State/Territory reserves, listed threatened, migratory and marine species and listed threatened ecological communities. Mapping of Commonwealth land is not complete at this stage. Maps have been collated from a range of sources at various

Not all species listed under the EPBC Act have been mapped (see below) and therefore a report is a general guide only. Where available data supports mapping, the type of presence that can be determined from the data is indicated in general terms. People using this information in making a referral may need to consider the qualifications below and may need to seek and consider other For threatened ecological communities where the distribution is well known, maps are derived from recovery plans, State vegetation maps, remote sensing imagery and other sources. Where threatened ecological community distributions are less well known, existing vegetation maps and point location data are used to produce indicative distribution maps. For species where the distributions are well known, maps are digitised from sources such as recovery plans and detailed habitat studies. Where appropriate, core breeding, foraging and roosting areas are indicated under 'type of presence'. For species whose distributions are less well known, point locations are collated from government wildlife authorities, museums, and non-government organisations; bioclimatic distribution models are generated and these validated by experts. In some cases, the distribution maps are based solely on expert knowledge. Only selected species covered by the following provisions of the EPBC Act have been mapped: - migratory and - marine The following species and ecological communities have not been mapped and do not appear in reports produced from this database: - threatened species listed as extinct or considered as vagrants - some species and ecological communities that have only recently been listed - some terrestrial species that overfly the Commonwealth marine area - migratory species that are very widespread, vagrant, or only occur in small numbers The following groups have been mapped, but may not cover the complete distribution of the species: - non-threatened seabirds which have only been mapped for recorded breeding sites - seals which have only been mapped for breeding sites near the Australian continent Such breeding sites may be important for the protection of the Commonwealth Marine environment.

Acknowledgements This database has been compiled from a range of data sources. The department acknowledges the following custodians who have contributed valuable data and advice: -Department of Environment, Climate Change and Water, New South Wales -Department of Sustainability and Environment, Victoria -Department of Primary Industries, Parks, Water and Environment, Tasmania -Department of Environment and Natural Resources, South Australia -Parks and Wildlife Service NT, NT Dept of Natural Resources, Environment and the Arts -Environmental and Resource Management, Queensland -Department of Environment and Conservation, Western Australia -Department of the Environment, Climate Change, Energy and Water -Birds Australia -Australian Bird and Bat Banding Scheme -Australian National Wildlife Collection -Natural history museums of Australia -Museum Victoria -Australian Museum -SA Museum -Queensland Museum

-Online Zoological Collections of Australian Museums -Queensland Herbarium -National Herbarium of NSW -Royal Botanic Gardens and National Herbarium of Victoria -Tasmanian Herbarium -State Herbarium of South Australia -Northern Territory Herbarium -Western Australian Herbarium -Australian National Herbarium, Atherton and Canberra -University of New England -Ocean Biogeographic Information System -Australian Government, Department of Defence -State Forests of NSW -Other groups and individuals

The Department is extremely grateful to the many organisations and individuals who provided expert advice and information on numerous draft distributions.

Please feel free to provide feedback via the Contact Us page.

© Commonwealth of Australia Department of Sustainability, Environment, Water, Population and Communities GPO Box 787 Canberra ACT 2601 Australia +61 2 6274 1111 Data from the BioNet Atlas of NSW Wildlife website, which holds records from a number of cust Species listed under the Sensitive Species Data Policy may have their locations denatured (^ ro Copyright the State of NSW through the Office of Environment and Heritage.

Report generated on 2/06/2012 7:39 PM Class Family Scientific Name Amphibia Hylidae Litoria aurea Aves Diomedeidae Diomedea gibsoni Aves Diomedeidae Thalassarche cauta Aves Procellariidae Pterodroma nigripennis Aves Ardeidae Botaurus poiciloptilus Aves Accipitridae ^^Lophoictinia isura Aves Accipitridae Hieraaetus morphnoides Aves Accipitridae Pandion cristatus Aves Haematopodidae Haematopus fuliginosus Aves Haematopodidae Haematopus longirostris Aves Charadriidae Thinornis rubricollis Aves Cacatuidae ^^Callocephalon fimbriatum Aves Cacatuidae ^Calyptorhynchus lathami Aves Psittacidae ^^Lathamus discolor Aves Psittacidae Glossopsitta pusilla Aves Strigidae ^^Ninox connivens Aves Strigidae ^^Ninox strenua Aves Tytonidae ^^Tyto novaehollandiae Aves Meliphagidae Epthianura albifrons Aves Neosittidae Daphoenositta chrysoptera Aves Pachycephalidae Pachycephala olivacea Aves Petroicidae Melanodryas cucullata cucullata Aves Petroicidae Petroica boodang Aves Petroicidae Petroica phoenicea Aves Estrildidae Stagonopleura guttata Mammalia Dasyuridae Dasyurus maculatus Mammalia Phascolarctidae Phascolarctos cinereus Mammalia Petauridae Petaurus australis Mammalia Potoroidae Potorous tridactylus Mammalia Pteropodidae Pteropus poliocephalus Mammalia Vespertilionidae Falsistrellus tasmaniensis Mammalia Vespertilionidae Miniopterus schreibersii oceanensis Mammalia Vespertilionidae Scoteanax rueppellii Mammalia Dugongidae Dugong dugon Mammalia Otariidae Arctocephalus forsteri Mammalia Otariidae Arctocephalus pusillus doriferus Mammalia Balaenopteridae Megaptera novaeangliae Mammalia Physeteridae Physeter macrocephalus Flora Araliaceae Astrotricha sp. Wallagaraugh Flora Rhamnaceae Pomaderris bodalla Flora Rutaceae Leionema ralstonii odians. ounded to 0.1°; ^^ rounded to 0.01°).

Common Name Legal Status Green and Golden Bell Frog E1 Gibson's Albatross V Shy Albatross V Black-winged Petrel V Australasian Bittern E1 Square-tailed Kite V Little Eagle V Eastern Osprey V Sooty Oystercatcher V Pied Oystercatcher E1 Hooded Plover E4A Gang-gang Cockatoo V Glossy Black-Cockatoo V Swift Parrot E1 Little Lorikeet V Barking Owl V Powerful Owl V Masked Owl V White-fronted Chat V Varied Sittella V Olive Whistler V Hooded Robin (south-eastern form) V Scarlet Robin V Flame Robin V Diamond Firetail V Spotted-tailed Quoll V Koala V Yellow-bellied Glider V Long-nosed Potoroo V Grey-headed Flying-fox V Eastern False Pipistrelle V Eastern Bentwing-bat V Greater Broad-nosed Bat V Dugong E1 New Zealand Fur-seal V Australian Fur-seal V Humpback Whale V Sperm Whale V Merimbula Star-hair E1 Bodalla Pomaderris V Ralston's Leionema V AECOM Merimbula Effluent Management Options Investigation Ecological Assessment of the Potential Impacts on Merimbula Lake from Shallow Dunal Exfiltration of Effluent

Appendix C

Flora and Fauna of Merimbula Lake - 1984

6 March 2013 AECOM Merimbula Effluent Management Options Investigation C-1 Ecological Assessment of the Potential Impacts on Merimbula Lake from Shallow Dunal Exfiltration of Effluent

Appendix C Flora and Fauna of Merimbula Lake - 1984 List of aquatic macrophytes and invertebrate animals recorded in Merimbula Lake estuary (1984) Rocks and Saltmarshes Intertidal Phylum Genus-species oyster and Subtidal sandy mud racks mangroves Chlorophyta (Green Acetabularia sp. Rare algae, green Mermaid’s cup (?) seaweeds) Cladophora sp. Common Codium sp. Rare (arborescent) Codium sp. Common Codium sp. Rare (prostrate) Ulva intestinalis Abundant Abundant (formerly Enteromorpha) Ulva lactuca Sea Abundant Abundant lettuce Heterokontophyta Colpomenia sinuosa Common (Brown algae, (ephiphytic) Sinuous brown seaweeds) ballweed Dictyota sp. Common Forkweed Hormosira banksii Abundant Neptune’s necklace Rhodophyta (Red Sargassum sp. Fairly common algae, red Laurencia sp. Common seaweeds) Lophosiphonia sp. Common Polysiphonia sp. Fairly common Thuretia sp. Rare Magnoliophyta Aegiceras Fairly common corniculatum River mangrove Avicennia marina Abundant Grey mangrove Halophila ovalis Abundant Abundant Paddle grass Juncus kraussii Sea Abundant rush Phragmites australis Abundant Common reed Sarcocornia Abundant quinqueflora Beaded glasswort Posidonia australis Abundant Strap grass Bolboschoenus Rare caldwellii (cited as Scirpus maritimus) Selliera radicans Rare Selliera Spergularia rubra Fairly common Sand spurry

6 March 2013 AECOM Merimbula Effluent Management Options Investigation C-2 Ecological Assessment of the Potential Impacts on Merimbula Lake from Shallow Dunal Exfiltration of Effluent

Rocks and Saltmarshes Intertidal Phylum Genus-species oyster and Subtidal sandy mud racks mangroves Sporobolus Common Common virginicus Saltwater couch Triglochin striata Fairly common Streaked arrowgrass Typha sp. Cumbungi Rare Zostera capricorni Abundant Abundant Eelgrass Zostera muelleri Common Eelgrass Cnidaria Actinia ?tenebrosa Rare ?Hydractinia Fairly common ?Edwardsiidae Rare Rare Phoronida Phoronis Fairly Fairly common albomaculata common Phoronis Fairly Rare psammophila common Phoronopsis harmier Common Fairly common Sipuncula Phascolosoma Rare Rare annulatum Polychaeta: errantia Ancistrosyllis cf. Rare constricta Australonereis abundant ehlersi Brania clavata rare Ceratonereis abundant common pseudoerythraeensis Ceratonereis common fairly common mirabilis Eulalia (Eumid) rare sanguinea Eunice antennata rare rare Exogone cf. rare Verugera Glycera americana rare rare Glyera tesselata rare rare Harmothoe common common praeclara Lumbrineris rare coccinea Lumbrineris latreilli common abundant Lumbrineris tetraura rare fairly common Lysidice natalenis rare Marphysa rare macintoshi Marphysa sanguine rare Rare Nematonereis rare unicronis Nephtys abundant common australiensis

6 March 2013 AECOM Merimbula Effluent Management Options Investigation C-3 Ecological Assessment of the Potential Impacts on Merimbula Lake from Shallow Dunal Exfiltration of Effluent

Rocks and Saltmarshes Intertidal Phylum Genus-species oyster and Subtidal sandy mud racks mangroves Nepthys longipes fairly common Nereis (Neanthes) rare acuminata Nereis (Neanthes) rare vaalii Ophiodromus sp. rare rare Paralepidonotus rare ampulliferus Perinereis nuntia fairly common brevicirris Perinereis obfuscata rare Phyllodoce rare rare (Anaitides) ?australis Pionosyllis rare ehlersiaeformis Platynereis australis rare Platynereis dumerilii rare Protodorvillea sp. 1 rare Pseudonereis rare variegata Schistomeringos rare rare rudolphi Sigalion ovigerum fairly common Sphaerosyllis rare semiverrucosa Syllis (Typosyllis) rare rare armillaris Syllis (Typosyllis) rare hyaline Polychaeta: Aonides oxycephala rare Rare Sedentaria Armandia intermedia fairly common fairly common Barantolla lepte common common Boccardia chilensis rare Capitella capitata rare rare Caulleriella rare tricapillata Chaetopterus rare variopedatus Cirriformia fairly common rare chrysoderma nuchalis Cirriformia filigera abundant Cirriformia fairly common abundant tentaculata Euclymene trinalis rare Galeolaria Abundant caespitosa Heteromastus fairly common fairly common filiformis

6 March 2013 AECOM Merimbula Effluent Management Options Investigation C-4 Ecological Assessment of the Potential Impacts on Merimbula Lake from Shallow Dunal Exfiltration of Effluent

Rocks and Saltmarshes Intertidal Phylum Genus-species oyster and Subtidal sandy mud racks mangroves Janua (Dexiospira) abundant brasiliensis Janua (Dexiospira) abundant steueri Magelona cf. pitelkai rare fairly common Mediomastus common common californiensis Mesochaetopterus rare ?saggitttarius Terebella sp. nov. fairly common rare Notomastus fairly common rare rare torquatus Owenia fusiformis fairly common rare Phylo felix rare Pista typha common common Polydora socialis fairly common Polyophthalmus rare pictus Pomatoceros rare rare caeruleus Prionospio rare common (Aquilaspio) aucklandica Prionospio rare (Aquilaspio) multipinnulata Prionospio rare rare (Minuspio) cirrifera Pseudopolydora common kempi Rhinothelepus rare macer Samythella sp. rare Scoloplos cylindrifer rare Scoloplos simplex common Spio pacifica rare Terebella cf. rare rare Ehrenbergi Cirripedia Balanus variegatus rare var. cirratus Balanus trigonus rare Chthmalus rare antennatus Elminius modestus abundant Tetraclitella fairly purpurascens common Amphipoda Aora MER 312 H rare Aoroides MER 148 rare rare Y Corophium MER 93 rare rare K

6 March 2013 AECOM Merimbula Effluent Management Options Investigation C-5 Ecological Assessment of the Potential Impacts on Merimbula Lake from Shallow Dunal Exfiltration of Effluent

Rocks and Saltmarshes Intertidal Phylum Genus-species oyster and Subtidal sandy mud racks mangroves Cymadusa sp.1 common abundant MER 93 J Cymadusa sp.2 common MER 235 Y Exoediceros fossor abundant rare Exoediceros sp. rare MER 56 C Eusiridae ? gen rare MER 301 J Haustoriidae gen. M fairly common MER 3 D Haustoriidae gen. N rare MER 163 D Isaeidae MER 249 E rare Limnoporeia rare yarrague Maera sp. MER 289 rare L ?Megamphopus rare rare MER 93 P Melita MER 42 D rare rare rare ?Monoculodes MER common 195 N Oedicerotidae sp. A fairly common MER 207 K Oedicerotidae sp. C fairly common MER 220 Z Oedicerotidae sp. 1 rare rare MER 275 O Oedicerotidae sp. 2 rare MER 279 D Orchestia chilensis rare MER 5 A Orchestia sp. 2 MER rare 96 E Paracalliope sp. rare rare MER 24 D Phoxecephalidae A abundant abundant MER 241 C Phoxecephalidae B abundant MER 275 P ?Podoceropsis sp. rare rare MER 73 F ?Talitroides MER rare 172 A Talorchestia sp. fairly common MER 308 B Tethygeneia sp. rare Urohaustorius abundant metungi Isopoda Actaccia pallida abundant Cirolana cf. arcuata abundant

6 March 2013 AECOM Merimbula Effluent Management Options Investigation C-6 Ecological Assessment of the Potential Impacts on Merimbula Lake from Shallow Dunal Exfiltration of Effluent

Rocks and Saltmarshes Intertidal Phylum Genus-species oyster and Subtidal sandy mud racks mangroves Deto marina rare Codonophilus cf. rare imbricatus Ligia australiensis rare Mesanthura sp. rare MER 272 Q Nerocila macleayi rare Paridotea ungulate rare rare Mysidacea Gastrosaccus dakini rare Decapoda: Macrura Alpheus sp. fairly common fairly common Macrobrachium abundant intermedium Palaemon affinis rare Penaeus plebejus rare rare Decapoda: Callianassa arenosa fairly common rare Anomura Callianassa fairly common australiensis Diogenes custos fairly common Decapoda: Brachynotus rare rare Brachyura spinosus Carinus ? maenas rare rare Cyclograpsus rare audouinii Halicarcinus cf. rare rare ovatus Halicarcinus fairly common rare paralacustris Heloecius fairly common cordiformis Helograpsus common haswellianus Mictyris longicarpus abundant Mictyris platycheles abundant Ovalipes rare australiensis Pachygrapsus rare laevimanus Paragrapsus laevis rare Pilumnopeus rare serratifrons Portunus pelagicus rare Sesarma common erythrodactyla Thalamita rare intermedia Thalamita sima rare Mollusca: Ischnochiton rare Polyplacophora elongatus crispus Bivalvia Ambuscintilla rare

6 March 2013 AECOM Merimbula Effluent Management Options Investigation C-7 Ecological Assessment of the Potential Impacts on Merimbula Lake from Shallow Dunal Exfiltration of Effluent

Rocks and Saltmarshes Intertidal Phylum Genus-species oyster and Subtidal sandy mud racks mangroves praemium Anadara trapezia rare common Arthritica helmsi abundant rare Bankia cf. carinata common Cyammiomactra cf. rare symmetrica Eumarcia fumigata common Fluviolanatus rare amarus Irus crenata rare Katelysia rhytiphora rare rare Katelysia scalarina rare Lasaea australis rare Laternula creccina rare rare Mesodesma rare elongate Musculus rare cumingianus Mysella sp. common common Mytilus edulis rare fairly common Notospisula rare rare trigonella Ostrea angasi rare Psammobia rare rare donacioides Saccostrea abundant commercialis Solemya velesiana rare Tapes cf. watlingi rare Tellina (Abranda) rare modestina Tellina (Macomona) common common deltoidalis Trichomya hirsuta rare common Wallucina assimilis common common Xenostrobus securis fairly common Gastropododa: Austrocochlea rare common fairly common Prosobranchia constricta Bedeva hanleyi rare fairly common Bembicium auratum abundant Bembicium rare melanostomum Bembicium nanum common abundant Bittium lacertinum rare abundant Patelloida mimula fairly common Cominella eburnea rare

6 March 2013 AECOM Merimbula Effluent Management Options Investigation C-8 Ecological Assessment of the Potential Impacts on Merimbula Lake from Shallow Dunal Exfiltration of Effluent

Rocks and Saltmarshes Intertidal Phylum Genus-species oyster and Subtidal sandy mud racks mangroves Diala sp. MER 31 J fairly common abundant Hydrobia rare abundant buccinoides Littorina scabra rare Littorina unifasciata common Montfortula rare conoidea Nassarius burchardi fairly common common Nassarius jonasii common fairly common Nerita airamentosa rare Neritina sp. MER rare 283 K Nodolittorina rare pyramidalis Patelloida alticostata rare Polinices (Conuber) rare sordidus Prothalotia rare fairly common comtessei Pseudoliotia micans fairly common rare Pyrazus ebeninus common Tatea kesteveni rare Tatea rufilabris rare Velacumantis rare australis Gastropoda: Akera soluta fairly common Opisthobranchia Aplysia cf. rare dactylomela Chemnitzia sp. MER rare 220 M Cingula spoina rare fairly common Odostomia sp. MER rare 219 X Gastropoda: Aclis MER 51 L, 58 rare Nudibranchia P Gastropoda: Ellisiphon cf. rare Pulmonata denticulatus Ophiocardelus quoyi fairly common Ophiocardelus rare sulcatus Onchidella patelloide rare Salinator fragilis abundant Salinator solida rare Cephalopoda Euprymna rare stenodactyla Idiosepius notoides rare Echinodermata Patriella exigua rare Amphipholis rare rare

6 March 2013 AECOM Merimbula Effluent Management Options Investigation C-9 Ecological Assessment of the Potential Impacts on Merimbula Lake from Shallow Dunal Exfiltration of Effluent

Rocks and Saltmarshes Intertidal Phylum Genus-species oyster and Subtidal sandy mud racks mangroves squamata Leptosynapta rare rare dolabrifera Syanptidae ?gen rare MER 285 T Chordata: rare Ascidiacea

List of fish recorded in Merimbula Lake (1984)

Scientific name Common Name Frequency Acantholeuteres spilomelanurus leather jacket rare Acanthopagrus australis yellow fin bream rare Acanthopagrus butcheri black bream rare Aldrichetta forsteri yellow-eyed mullet rare Ammotretis rostratus flounder rare Arenigobius befrenatus goby rare Argyrosomus hololepidotus mulloway rare Centropogon australis fortesque fairly common Chrysophrys auratus snapper rare Cheilinus bimaculatus wrasse rare Cristiceps australis crested weedfish rare Enoplosus armatus oldwife rare Favonigobius lateralis long finned goby rare Favonigobius tamarensis Tamar river goby rare Girella tricuspidata blackfish common Gobiopterus semivestitus transparent goby rare Hippocampus abdominalis seahorse rare Hyporhamphus australis garfish rare Lethrinus nematacanthus scavenger rare Meuschenia freycineti leather jacket fairly common Meuschenia hippocrepis variable leather jacket rare Meuschenia trachylepis MER 105 E rare Monacanthus chinensis fan bellied leather jacket rare Mugil cephalus sea mullet rare Mugil georgii fantail mullet rare Mugilidae juveniles abundant Muraenichthys australis worm eel rare Myxus elongatus sand mullet rare Neoodax balteatus little rock whiting rare Nesogobius pulchellus pretty goby common Nesogobius sp. MER 278 T goby rare Ophisurus serpens snake eel rare Parkraemia ornata ornate goby rare Penicipelter vittiger leather jacket rare

6 March 2013 AECOM Merimbula Effluent Management Options Investigation C-10 Ecological Assessment of the Potential Impacts on Merimbula Lake from Shallow Dunal Exfiltration of Effluent

Scientific name Common Name Frequency Petroscirtes lupus blenny rare Platycephalus fuscus dusky flathead common Platycephalus laevigatus smooth flathead rare Platycephalus marmoratus marbled flathead rare Pomatomus saltatrix tailor rare Pranesus ogilbyi hardyhead rare Pseudogobius olorum Swan river goby rare Redigobius macrostoma large mouthed goby rare Rhabdosargus sarba tarwhine rare Scorpaena cf. cruenta rock cod rare Sillago ciliata sand whiting fairly common Sillago maculate trumpeter whiting rare Stethojulis interrupta wrasse rare Stigmatophora argus spotted pipefish abundant Stigmatophora nigra pipefish abundant Syngnathus phillipi pipefish rare Torquigener glaber puffer rare Torquigener hamiltoni puffer rare Urocampus carinirostris pipefish rare Usacaranx georgianus trevally abundant Vincentia charysurus cardinal fish rare

6 March 2013 AECOM Merimbula Effluent Management Options Investigation C-11 Ecological Assessment of the Potential Impacts on Merimbula Lake from Shallow Dunal Exfiltration of Effluent

Aquatic birds recorded in 1974-76 in Merimbula Lake (1984)

Scientific name Common name Frequency Habits Food Anas superciliosa black duck fairly common in dabbler invertebrates spring and algae Ardea novaehollandiae white faced heron common in Spring wader fish and crustacea Calidris ferruginea curlew sandpiper rare in summer wader on sand Invertebrates and mud Cygnus atratus black swan common in spring swimmer grazes on Zostera etc Egretta garzetta little egret fairly common in wader fish and spring crustacea Haematopus fuliginosus sooty oystercatcher frequent in spring wader on rocks invertebrates and oyster racks Haematopus longirostris pied oystercatcher common in spring wader on sandy mainly mud crustacean fish Larus novaehollandiae silver gull common in spring Scavenges on general shores and carnivore shallows Limosa lapponica bar-tailed godwit common in spring wader on mud mainly and summer polychaetes Numenius eastern curlew common in spring wader on mud in invertebrates madagascariensis and summer mangroves Phalacrocarax carbo black cormorant common in spring swimmer and fish diver Phalacrocarax little pied cormorant common in spring swimmer and fish melanoleucos diver Phalacrocarax sulcirostris little black cormorant occasional in spring swimmer and fish diver Sterna bergii crested tern common in spring plunge dives fish

6 March 2013 AECOM Merimbula Effluent Management Options Investigation Ecological Assessment of the Potential Impacts on Merimbula Lake from Shallow Dunal Exfiltration of Effluent

Appendix D

Supplementary Report (Elgin Associates, 2013)

6 March 2013 `

FINAL REPORT Prepared for Bega Valley Shire Council Zingel Place, Bega

5 March 2013 PROJECT REFERENCE: JN12073

Elgin Associates Pty Ltd ABN 59123488639

Document Information

Author (s): Dr Nicholas Yee

Andrew Roberts

Project Manager: Dr Nicholas Yee

Date: 5 March 2013 Reviewed by: Andrew Roberts Status: FINAL

Filename: JN12073_R100c

Project: Elgin JN12073 Supplementary Report

Contact: Elgin Associates Pty Ltd ABN 59123488639 Level 1, 45-47 Church Street, PO Box 829 Bega, New South Wales, 2550 Telephone: +61 400 365 234 Fax: +61 3 86486336 www.elgin.com.au

Record of Report Distribution

No of Status Date Prepared for: copies

1 digital Draft 12 February 2013 BVSC

1 digital Draft 28 February 2013 BVSC

1 digital Final 5 March 2013 BVSC

© Elgin Associates Pty Ltd

* Elgin Associates Pty Ltd (Elgin Associates) has prepared this document for the purpose which is described in the Scope of Works section, and was based on information provided by the client, Elgin Associates understanding of the site conditions, and Elgin Associates experience, with regard to the assumptions that Elgin Associates can reasonably be expected to make in accordance with sound professional principles.

* This document was prepared for the sole use of the party identified on the cover sheet, and that party is the only intended beneficiary of Elgin Associates work.

* No other party should rely on the document without the prior written consent of Elgin Associates, and Elgin Associates undertakes no duty to, nor accepts any responsibility to, any third party who may rely upon this document.

* All rights reserved. No section or element of this document may be removed from this document, extracted, reproduced, electronically stored or transmitted in any form without the prior written permission of Elgin Associates.

EXECUTIVE SUMMARY

Elgin Associates Pty Ltd (Elgin Associates) was engaged by Bega Valley Shire Council (BVSC) to undertake a supplementary study for the - ‘Ecological Assessment of the potential impacts on Merimbula Lake from dunal ex-filtration of effluent’. Information provided in this report specifically reviews the potential impact that increased freshwater and nutrient flux may have on the ecological values of the lake and more specifically, what responses may be expected from estuarine vegetation at the site.

This information includes:

• Confirmation of and description of vegetation communities at the site;

• Qualitative discussion regarding the hydrodynamics of Merimbula Lake;

• The current ecological condition and surface water quality of Merimbula Lake;

• Factors that could influence the response of vegetation communities to increased nutrient flux; and

• Local case study of increased nutrient supply to an estuarine setting.

IGGC (2013) modelled groundwater flow mass balance for year 2025 estimated effluent disposal volumes via a 400 metre exfiltration trench located within BVSC land in the dunes east of Merimbula airport. Model outcomes predict a net increase in groundwater discharge to Merimbula Lake of approximately 7.5%, occurring within an area of approximately 28,000 m2 on the eastern side of the lake. Under scenarios 2 and 4 of the four scenarios modelled by IGCC (2013) using year 2025 estimated effluent disposal volumes, steady state concentrations of nitrogen (mostly as bioavailable NO3) and phosphorous (mostly as bioavailable PO4) were predicted to be discharged from the lake bed after 15 to 27 years, respectively. Under scenarios 1 and 3 neither nitrate nor phosphate from effluent reach the lake in groundwater within the 57 year modelled period.

For scenarios 2 and 4, tidal flushing will dilute and reduce the concentration of nitrogen and phosphorous discharging within groundwater within the identified discharge plume area and transport these nutrients to other regions of the lake. Nevertheless, this discharge of nutrients from sediment porewater would represent a new continuous supply of inorganic N and P in bioavailable forms that has the potential to further stimulate existing levels of primary production at the site and within the lake generally. A potentially vulnerable area of the lake to increased supply of bioavailable nutrients is the backwater Golf Course Lake due to its reduced capacity for flushing and estimated longer water residence times

ii

TABLE OF CONTENTS

EXECUTIVE SUMMARY.………………………………………………………………………………………………………………………..II TABLE OF CONTENTS……………………………………………………………………………………………………….…………………IV LIST OF TABLES DRAWINGS AND APPENDICES………….……………………………………………………..……………………….V LIST OF ABBREVIATIONS AND ACRONYMS……………………………………………………………………………………….…..….VI GLOSSARY……………………………………………………………………………………………………………………………………… VII 1 INTRODUCTION ...... 8

1.1 BACKGROUND ...... 8

1.2 SUMMARY OF IGGC (2013) MODELLING ...... 9 1.2.1 Groundwater Discharge to Receiving Waters ...... 10 1.2.2 Nutrient Transport and Flux ...... 10

1.3 ASSESSMENT OF ECOLOGICAL IMPACT ...... 13

1.4 SCOPE OF WORK ...... 13 2 METHODOLOGY ...... 14

2.1 SITE INSPECTION ...... 14 2.1.1 Algal samples ...... 15 2.1.2 Voucher specimens ...... 15 2.1.3 Field photos ...... 15

2.2 DESKTOP REVIEW ...... 15 3 RESULTS AND DISCUSSION ...... 16

3.1 SITE INSPECTION ...... 16 3.1.1 General Observations ...... 16 3.1.2 Seagrass ...... 16 3.1.3 Mangrove and Saltmarsh ...... 17 3.1.4 Macroalgal assemblages and substrates ...... 17 3.1.5 Microalgal assemblages and substrates ...... 18 3.1.6 Faunal burrows ...... 18 3.1.7 Tidal Flows and Hydraulic Mixing ...... 18

3.2 CURRENT ECOLOGICAL CONDITION OF MERIMBULA LAKE ...... 21 3.2.1 2010 State of Catchments Report (DECCW 2011) ...... 21 3.2.2 Surface Water Quality of Merimbula Lake ...... 22

3.3 RESPONSE OF VEGETATION COMMUNITIES TO INCREASED NUTRIENT FLUX ...... 24 3.3.1 Nutrient limitation ...... 24 3.3.2 Benthic and Pelagic microalgae ...... 24 3.3.3 Macroalgae ...... 25 3.3.4 Saltmarsh ...... 26 3.3.5 Seagrass ...... 27

3.4 LOCAL CASE STUDY OF INCREASED NUTRIENT SUPPLY TO AN ESTUARINE SETTING ...... 27 4 CONCLUSIONS ...... 29 5 REFERENCES ...... 31 6 LIMITATIONS ...... 33

iv

LIST OF TABLES, DRAWINGS & APPENDICES

LIST OF TABLES (IN TEXT)

Table 1 Predicted phosphate and nitrate concentrations for modelled discharge zones

Table 2 Transect coordinates

Table 4 Estimated tidal discharge at Merimbula causeway, 25 October 2003

Table 5 Estimated water volumes overlying sediments at the site at mean low and mean high tide.

Table 6 MER environmental indicators for assessment of estuarine ecological health

Table 7 Mean water column nutrients and properties for Merimbula Lake

LIST OF TABLES (ATTACHED)

Table 3 Macroalgae recorded during the site inspection

LIST OF FIGURES (ATTACHED/IN TEXT)

Figure 1 Overview of the area of investigation

Figure 2 Study Site (attached)

Figure 3 Estuarine vegetation and survey transects inspected (attached)

Figure 4 Survey transects (attached)

Figure 5 Generalised flushing duration periods predicted for areas of Merimbula Lake

LIST OF APPENDICES

Appendix A IGGC (2013) Figures 13.11a-13.11f

Appendix B Images from field inspection – 21 December 2012

Appendix C Tidal prism Merimbula Lake – 25 October 2003

Appendix D Examples of algae known to bloom in Merimbula Lake

v

LIST OF ABBREVIATIONS AND ACRONYMS

ANZECC Australia and New Zealand Environment Conservation Council BVSC Bega Valley Shire Council Chl a chlorophyll a DO Dissolved oxygen DECCW NSW Department of Environment and Climate Change Water EC Electrical conductivity FRP Filterable Reactive Phosphate (also known as ortho-phosphate)

Kd Partition coefficient Km2 Kilometers squared m2 Metres squared mg/L Milligrams per litre + NH4 ammonium - - NOx Oxides of nitrogen including nitrate (NO3 )and nitrite (NO2 ) NTU Nephelometric Turbidity Units

Kd Partition coefficient OEH NSW Office of Environment and Heritage pH Measure of the acidity or alkalinity of a solution SEPP State Environment Protection Policy STP Sewage treatment plant t Tonne TDS Total Dissolved Solids TKN Total Kjeldahl Nitrogen (all organic forms of nitrogen) TN Total Nitrogen (all forms of N) TP Total Phosphorous (all forms of P) TSS Total Suspended Solids μg/L Micrograms per litre μM Micromolar N/A Not Applicable

vi

GLOSSARY

reworking of sediment causing displacement and mixing of sediment bioturbation particles and porewater through burrowing activity

the process of benthic organisms flushing their burrows with overlying bioirrigation water

in context of this report - the rate of transport of materials from the flux sediments to the overlying water column (refer Fick’s Law)

Partition distribution coefficient – a parameter used to estimate the Kd migration potential of contaminants present in aquaeous solutions in contact with surface, subsurface and suspended solids. the microscopic, photosynthetic eukaryotic algae and cyanobacteria that microphytobenthos live on seafloor habitats ranging from wave swept beaches to detritus- laden backwater lagoons. the algal body; also used in relation to other simply constructed, non- thallus vascular plants; plural thalli.

vii

INTRODUCTION

1 INTRODUCTION Elgin Associates Pty Ltd (Elgin Associates) was engaged by Bega Valley Shire Council (BVSC) to undertake a supplementary study to support the - ‘Ecological Assessment of the potential impacts on Merimbula Lake from dunal ex-filtration of effluent’ study being undertaken by AECOM consultants.

This supplementary study provides information regarding the vegetation communities and algal taxa present in the area, referred to herein as ‘the site’, that modelling by IGGC (2013) shows may be affected by the discharge of nutrient-enriched groundwater should effluent disposal by dunal exfiltration proceed within the dunes east of Merimbula airport. Particular attention is given to algal communities present at the site and in the lake more broadly, as prolific algal growth is typically the first indication of excess nutrients becoming a problem. Finally, the potential impacts of increased nutrient flux on the ecology of Merimbula Lake is considered given the data available and patterns observed in estuarine settings elsewhere in the region and in Australia more broadly.

1.1 Background BVSC engaged AECOM in 2009 to investigate, identify and assess options for the beneficial use of effluent and disposal of that proportion of flows unable to be beneficially used (excess effluent) from the Merimbula sewage treatment plant (STP). The outcome of the options investigation is to form a strategy for effluent management that provides the greatest benefit to the community and environment, whilst being affordable.

A range of investigations have been undertaken to identify options for the disposal of effluent from the STP including the construction of an exfiltration system within the Merimbula-Pambula dunal system to allow effluent to exfiltrate into the dunal aquifer. This option would result in groundwater near an exfiltration system being recharged by effluent in addition to rainwater resulting in an increase in the natural volume and flow of groundwater towards the ocean and the lake.

Groundwater flow modelling (IGGC 2013) for year 2025 estimated effluent disposal volumes via a 400 metre exfiltration trench located within BVSC land in the dunes east of Merimbula airport indicates that the majority of effluent disposed would flow in groundwater towards the ocean (approximately 81%) and the remainder would flow westward towards Merimbula Lake. Further modelling was undertaken by IGGC (2013) to assess the potential for phosphorous (P) and nitrogen (N) in effluent to migrate in groundwater to Merimbula Lake and the ocean. Four scenarios were modelled with discharge flux rates and typical nitrogen and phosphorous concentrations in groundwater estimated for the identified discharge zones in the bay and lake for each scenario. The potential ecological impacts on the vegetations communities within predicted discharge zones is the subject of this supplementary report.

The approximate location of the ex-filtration trench used by IGGC (2013) for the groundwater flow and water quality modelling assessment is shown in Figure 1 with groundwater flow directions (drawn conceptually) and the area of the lake that was investigated during this study outlined.

8

INTRODUCTION

Figure 1. Overview of the area of investigation in relation to the Merimbula STP, the existing dunal exfiltration ponds and the location of the exfiltration trench used for the modelling assessment.

1.2 Summary of IGGC (2013) modelling A brief summary of the IGGC (2013) groundwater model output for year 2025 estimated effluent disposal volumes via a 400 metre exfiltration trench located as shown in Figure 1 is presented here to provide context for this report.

Four scenarios were modelled to examine existing (8.5 mg/L) and reduced (1.5 mg/L) phosphate concentrations present in discharged effluent from the STP, two Kd values for phosphorus sorption in the sediments and two R values for nitrate decay in the sediments. The outcomes of modelled Kd and R values are summarised conceptually in terms of best and worse cases below:

9

INTRODUCTION

Kd 0.1 mL/g------|------Kd 2.0 mL/g Low P sorption capacity Some P sorption capacity

-1 -1 R 0.0 day ------|------R 0.002 day No denitrifcation Some denitrification

worse case best case

The Kd value of 2.0 was obtained from testing of the dune sediments in the central dune region and is considered to provide a conservative estimate of the P sorption capacity of the dune material in the area of the exfiltration system shown in Figure 1. The Kd value of 0.1 is considered to provide a worst-case estimate for phosphate removal (IGGC 2013).

The R value of 0.002 was obtained from calibration of a simple numeric model of groundwater flow and total inorganic nitrogen concentrations in two groundwater monitoring bores near to the existing effluent ponds. It represents a conservative first-order decay reaction estimate of nitrate removal by denitrification. The R value of 0 is considered to provide a worst-case estimate for nitrate removal (IGGC 2013).

Models were based on a 57 year simulation as this encompasses the realistic lifespan of an exfiltration system, that is likely to be 20 to 50 years (IGGC 2013).

The four scenarios modeled were:

Scenario 1 High P as Phosphate in effluent (8.5 mg/L) and Low Kd (2.0), R (NO3) = 0.002

Scenario 2 High P as Phosphate in effluent (8.5 mg/L) and Very Low Kd (0.1), R (NO3) = 0

Scenario 3 Low P as Phosphate in effluent (1.5 mg/L) and Low Kd (2.0), R (NO3) = 0.002

Scenario 4 Low P as Phosphate in effluent (1.5 mg/L) and Very Low Kd (0.1), R (NO3) = 0

1.2.1 Groundwater Discharge to Receiving Waters Effluent disposal via an exfiltration trench in the location shown in Figure 1 results in an overall increase in net groundwater discharge to receiving waters. For year 2025 estimated disposal volumes in this location, the greatest increase in groundwater discharge would occur to the ocean, with a total net increase 73% higher than under natural conditions. The total net increased discharge to the lake is estimated at 7.5% higher than under natural conditions. Modelling estimates groundwater to travel from the exfiltration trench to the lakeshore in approximately 7 years, with typical travel times of 12 years or more prior to lake-bed discharge. There is a clear decrease in groundwater velocity once the lakeshore is reached reflecting the low hydraulic gradient in the shallow aquifer beneath the lake (IGGC 2013).

1.2.2 Nutrient Transport and Flux IGGC (2013) model output included figures showing typical N and P concentrations in groundwater that can be expected for the identified discharge zones (shore and near-shore) in

10

INTRODUCTION

the lake and ocean for each scenario. Figures showing nutrient concentration pathlines and the areas of the lakeshore affected are contained in Appendix A.

Under scenarios 1 and 3, where a conservative decay reaction estimate for nitrate removal (R =

0.002) and a conservative phosphorous sorption capacity of the sediments (Kd = 2.0) is assumed, modelling shows nitrate and phosphate from effluent disposal does not reach the lakeshore, irrespective of P concentration being 8.5 mg/L or 1.5 mg/L in effluent.

However, under scenario 2, where no decay rate for nitrate (R = 0) is assumed and the phosphorous sorption capacity of the sediments is assumed very low (Kd = 0.1), nitrate and phosphate is predicted to reach the lakeshore and discharge from the lake-bed. Scenario 2 represents a “worse-case” and predicts that nitrate will reach the lake-bed along 1,700 m of shoreline within 3 years with the discharge plume extending up to 250 m from the shore and reach a steady state discharge concentration of 0.8 mg/L within the near shore zone within 15 years. Phosphate is predicted to reach the lake-bed along 1,800 m of shoreline within 5.5 years with the discharge plume extending up to 220 m from the shore and reach a steady state discharge concentration of 2.5 mg/L within the near shore zone within 27 years.

For all scenarios, an increased volume of freshwater will also discharge from the lake-bed. Predicted nutrient discharge concentrations, the lake area affected determined from the modelling and equivalent flux rates are summarised in Table 1 (below).

11

INTRODUCTION

Table 1. Predicted phosphate and nitrate concentrations for modelled discharge zones and equivalent flux rates (based on data from Table 13.6, 13.10 & 13.11 in IGGC 2013).

Lake Shore1 Lake Near Shore

Scenario Nutrient Nutrient Nutrient Nutrient Mean conc. (mg/L), Mean conc. (mg/L), flux rate2 flux rate2 flux rate flux rate Length (m) Area (m2) (g/day) (µmol/m2/hr) (g/day) (µmol/m2/hr)

Phosphate (as P)

1 0 mg/L, 0 m 0 - 0 mg/L, 0 m2 0 -

5 mg/L, 400 m 2 2,326 769 2.5 mg/L, 287,400 m2 961 10 1.5 mg/L, 1,400 m

3 0 mg/L, 0 m2 0 - 0 mg/L, 0 m2 0 -

0.8 mg/L, 400 m 4 426 158 0.3 mg/L, 153,100 m2 90 2 0.4 mg/L, 1200 m

Nitrate (as N)

1 0 mg/L, 0 m2 0 - 0 mg/L, 0 m2 0 -

1.4 mg/L, 400 m 2 724 253 0.8 mg/L, 242,400 m2 200 3 0.6 mg/L, 1,300 m

3 0 mg/L, 0 m2 0 - 0 mg/L, 0 m2 0 -

1.4 mg/L, 400 m 4 724 253 0.8 mg/L, 242,400 m2 200 3 0.6 mg/L, 1,300 m Note:

1 Lake Shore values provided represent inner and outer (values italicized) zones, coinciding with the constant head boundary (the central area with greatest flow and highest concentration) and the remainder, and indicate the linear distance along which increased nutrient flux is expected.

2 Nutrient flux rate (as g/day and ) represents total sum for both inner and outer lakeshore zones.

12

INTRODUCTION

1.3 Assessment of Ecological Impact In order to assess the relative impact of each of the simulated nutrient transport scenarios on the Lake’s ecology, the scenarios may be ordered in terms of best to worse case scenarios as follows:

Scenario Outcomes Best Case 1 & 3 increased freshwater flux only

4 increased freshwater, nitrate and low phosphate flux

2 increased freshwater, nitrate and high phosphate flux Worse Case

An assessment of ecological impact for each of these cases is being undertaken by AECOM (report in prep.). The purpose of this supplementary report is to provide additional data regarding the potential impact that increased freshwater and nutrient flux may have on the ecological values of the lake and more specifically, what responses may be expected from estuarine vegetation at the site.

1.4 Scope of Work In order to provide more site-specific information regarding how the vegetation communities and algae at the site may respond to increased levels of nutrients (N and P) due to groundwater discharge, the following scope of work was undertaken:

1) Background review of the IGGC (2013) report, and review relevant data regarding ecological condition of Merimbula Lake;

2) Conduct a site inspection to confirm what vegetation communities (saltmarsh, mangrove, seagrass and algae) and species are specifically present at the ‘site’;

3) Conduct a literature review regarding the vegetation communities and species found at the site, with qualitative discussions that include a focus on potential impacts of increased P and N nutrients; and

4) Preparation of this report containing the findings of the site inspection and literature review.

13

METHODOLOGY

2 METHODOLOGY 2.1 Site Inspection A field inspection of the site was undertaken after review of the following information:

• IGGC report (IGGC 2013); • estuarine vegetation mapping for Merimbula Lake (Creese et al. 2009); and • modelled nutrient (N and P) pathlines (IGGC 2013) showing the areas of the lake likely to be affected by increased concentrations of nutrients discharged via groundwater.

Review of this information informed the site inspection by defining the site boundary as shown in Figure 2 (attached). The extent of the site boundary was based on the nutrient distribution pathlines for the worse case scenario (i.e. Figures 9b and 9e in Appendix A). Estuarine habitat mapping by Creese et al. (2009) provides the most current assessment of vegetation distribution for Merimbula Lake including the site area.

Inspections were carried out from a small workboat with wading of most areas required due to the shallow depths encountered. The site inspections consisted of a combined haphazard and transect survey approach. Qualitative observations were recorded haphazardly over the site with detailed inspections conducted along six transects situated across the site area. Transect locations were spaced approximately 300 – 400 m apart and determined largely by the vegetation communities mapped by Creese et al. (2009). Transect locations with regard to the mapped vegetation communities are shown on Figure 3 (attached) with coordinates provided in Table 2.

Table 2. Transect coordinates

Transect Location Start End

36°54’21.16” S 36°54’30.02” S A1 Backwater entrance 149°53’37.11” E 149°53’36.14” E 36°54’21.96” S 36°54’31.63” S A2 Backwater entrance 149°53’40.21” E 149°53’38.65” E 36°54’09.32” S 36°54’14.89” S B Flood-ebb delta 149°53’38.78” E 149°53’45.45” E 36°54’02.72” S 36°54’8.94” S C Flood-ebb delta 149°53’52.02” E 149°53’58.21” E 36°53’57.01” S 36°54’4.45” S D Flood-ebb delta 149°54’10.50” E 149°54’13.53” E 36°53’52.45” S 36°53’58.31” S E Flood-ebb delta 149°54’20.43” E 149°54’24.41” E

Qualitative observations recorded during the inspection included:

• confirmation of mapped vegetation communities including seagrass, mangrove and saltmarsh communities; • diversity of algal taxa present; • presence of natural or artificial hard substrata that may be readily colonised by algae; and • presence of faunal burrows in benthic sediments.

GPS was used to locate the extent of the site and transect locations. Vegetation communities and algal taxa encountered were photographed with samples of macroalgae collected for further

14

METHODOLOGY

identification as required. A list of all saltmarsh, mangrove, seagrass and algal species present at the site during the field inspection as well as macroalgal taxa known to occur seasonally, though not encountered during the field inspection are presented in Section 3.1.2.

2.1.1 Algal samples Whole algal thalli were collected by hand into clean plastic containers with seawater, collection details logged and stored on ice. Samples were examined under light microscope at x200 and x400 magnification to determine genus and species identity where possible with portions of sample collections set aside for preservation as voucher specimens.

2.1.2 Voucher specimens Voucher specimens representative of each sample collection were preserved with 4% formalin- seawater solution in 5 ml vials and or pressed on herbarium paper to be lodged at the National Herbarium of NSW.

2.1.3 Field photos Images of vegetation types, substrates and macroalgae observed at the site were recorded using a waterproof Panasonic Lumix FT-3 camera.

2.2 Desktop Review A literature review was undertaken for each of the vegetation communities and algal taxa found during the site inspection with a focus on responses to elevated levels of N and P nutrients. Factors considered for this review included:

• Physiological constraints i.e. species growth limited by N or P? • Nutrient uptake rates i.e. slow growing versus fast growing species • Is the species an indicator of excessive nutrient inputs? i.e. fast growing species known to form blooms?

Locally relevant case study of an estuarine setting where excess nutrient inputs have occurred and the ecological consequences that have likely arisen due to those historical inputs is presented (i.e. Racecourse Creek, Bega River estuary).

15

RESULTS AND DISCUSSION

3 RESULTS AND DISCUSSION 3.1 Site Inspection A field inspection of the site was conducted on 21 December 2012 during ebb tidal conditions. According to tidal charts, low tide of 0.67 mAHD occurred at approximately 11:20 am at Merimbula bridge (~90 mins after tide predictions for Fort Dension, 08:50 am). Observations regarding substrates, vegetation type and occurrence of macroalgae were recorded along six transects as shown in Figure 4. Mangrove and saltmarsh habitats were inspected briefly to determine the most common taxa though transect surveys through these habitats were not specifically undertaken. Field images recorded during the site inspection and descriptions of vegetation communities and habitats are presented in Appendix B and support the information contained in the sections below.

3.1.1 General Observations The site, as defined in Figure 2, is approximately 0.41 km2 in area and part of the marine-tidal delta of the estuary. Greater than 50% of that area is characterised by sand-flats (0.23 km2 in area) that are either devoid of- or sparsely vegetated with seagrass.

3.1.2 Seagrass Three seagrass species were recorded at the site including Posidonia australis (strapweed), Halophila ovalis (paddleweed) and Zostera muelleri (eelgrass). While Zostera and Halophila are relatively common seagrasses, Merimbula Lake represents one of only five locations in the Bega Valley where Posidonia occurs. The other locations being Twofold Bay, Pambula Lake, Kianniny Bay and Bermagui River.

Sand flats where seagrasses are absent is due to regular exposure at low tide. Sand-flats that are sparsely vegetated, comprising the seagrasses Halophila ovalis and Zostera muelleri are exposed less frequently and become more densely vegetated with increasing water depth. The larger seagrass Posidonia australis is present at the deeper, permanently submerged, areas of the site.

The current distribution of Posidonia at the site is accurately represented by vegetation mapping in Figure 3 (from Creese et al. 2009). In contrast, the current distribution of the small seagrass Halophila ovalis is not accurately represented in Figure 3. Halophila is typically less than 7 cm high and was common across the site with discrete patches present in tidal channels close to the shoreline. The vegetation mapping depicted in Figure 3 is based on aerial imagery and field survey data that is now a decade-old. Halophila and Zostera are relatively fast growing seagrasses and patch sizes may vary on a yearly basis. In contrast, Posidonia is a slow growing seagrass and variation in patch sizes may only be detected over time-scales of decades or longer.

Mapping seagrass patches at the site was not part of this project scope. However, a seagrass landscape (including sparse and dense meadows) is conservatively estimated to cover more than 30% of the site area that is shown to be unvegetated in Figure 3. Overall, it is estimated that a seagrass landscape (including sparse and dense meadows) may cover as much as 0.25 km2, approximately 60% of the site. A quantitative assessment would need to be undertaken to accurately assess seagrass cover at the site.

16

RESULTS AND DISCUSSION

3.1.3 Mangrove and Saltmarsh A continuous band of grey mangroves (Avicennia marina) are present along the site shoreline. The specialised peg roots (pneumatophores) extend as much as 8 m from the shoreline into the intertidal zone. Sediments beneath the mangrove canopy are grey in color and release a sulphide odour when disturbed indicative of high organic content in the sediments.

Saltmarsh community occurs immediately behind the mangroves above the mean high water mark. The most conspicuous species in this community include samphire (Sarcocornia quinqueflora), coastal speargrass (Austrostipa stipoides), sea rush (Juncus krausii) and shrubby samphire (Tecticornia arbuscula). The saltmarsh community within the predicted discharge zone (as modelled in IGGC Figs 13.11b and 13.11f) covers approximately 0.54 km2. The most dominant species within the community would appear to be shrubby samphire (Tecticornia arbuscula) with coastal speargrass (Austrostipa stipoides), and sea rush (Juncus krausii) found adjacent to the mangroves and along drainage channels. Field images of mangrove and saltmarsh habitat at the site are contained in Appendix B.

3.1.4 Macroalgal assemblages and substrates Substrates at the site include sand flats, seagrass meadows, shell beds and oyster lease infrastructure (ropes, posts and baskets), each providing opportunities for the colonisation of macro- and microalgal assemblages.

A variety of macroalgae were present across the site, epiphytic on seagrass and attached to available natural and artificial hard substrata. While not quantitatively assessed, macroalgal epiphyte loads on seagrass were more conspicuous and appeared greater at the southern end of the site (Transects A1, A2 and B) compared to the northern end of the site (Transects C, D and E). The dominant epiphytic taxa on seagrass included four species of red algae (Laurenica majuscula var. elegans, Centroceras clavulatum, Spyrida filamentosa and Polysiphonia infestans) and two species of brown algae (Dictyota alternifida and Dictyota dichotoma). A full list of algal taxa recorded at the site is provided in Table 3 (attached).

The occurrence of natural hard substrates at the site is limited to the area in the vicinity of Transect B where old shell beds have been exposed and extend from 0.5 m depth to the lake shore. Oysters have also colonised the available hard substrate in this area. Artificial hard substrata at the site include the ropes, posts and floating baskets of the oyster leases located at the site margins. The green alga Codium and brown alga Dictyota had a preference for the ropes. Beyond the site boundary, the availability of hard substrates in Merimbula Lake is relatively limited. Rocky shore areas are scattered around the lake margins though majority of these areas are intertidal and do not favour the establishment of macroalgal assemblages. Subtidal rocky habitats do exist in the vicinity of the causeway and at the estuary entrance where larger macroalgal taxa such as the brown alga Sargassum sp. are common. However, although the lake environment is marine (salinity typically >34 ppt) it does not support kelps beds due to the lack of suitable rocky hard substrata.

17

RESULTS AND DISCUSSION

3.1.5 Microalgal assemblages and substrates Microalgal assemblages include pelagic (suspended in water column) phytoplankton and benthic microalgae, also known as the microphytobenthos. Phytoplankton at the site would be transient due to the strong tidal flows across the site. In contrast, a benthic microalgal assemblage would be ever-present creating biofilms on most substrates. This includes the sandy sediments where aggregations of benthic microalgae were noted around faunal burrows in the vicinity of Transect B (Appendix B – Plate 3). While this algal assemblage was not specifically examined, it is likely to consist mostly of diatoms (Class Bacillariophyceae). As water depths at the site are shallow and water clarity high, the microphytobenthos would play an important role in nutrient turnover at the site. Indeed, the pelagic and benthic microalgal assemblages represent an important component of the primary production and nutrient cycling for all parts of the estuary.

3.1.6 Faunal burrows Faunal burrows occur in the lower intertidal zone across the site and evidence of bioturbation was widespread. Burrowing fauna include crustaceans (crabs and shrimp), worms and bivalves and burrows may reach depths of 0.4 m. Faunal burrows increase the sediment-water interface and there is a wealth of evidence that burrowing activity (bioturbation) and the flushing of burrows by fauna (bioirrigation) can enhance the porewater-seawater exchange and thereby the release of nutrients from the bed, which may support primary production (Santos et. al. 2012). Aggregations of microalgae around burrows in the vicinity of Transect B indicate this is likely to be occurring at the site. At high densities, burrowing fauna may be the dominant process of porewater advective exchange (Santos et al. 2012). This could be important mechanism for enhancing the release of nutrients from the lake-bed to be flushed away from the immediate site by tidal currents.

3.1.7 Tidal Flows and Hydraulic Mixing Water depths across the site ranged from 0 to 0.6 m (at low tide of 0.67 mAHD) with average water depth considered to be ~0.3 m. Tidal flows across the shallow sand flats were strong (not measured) though tidal flows were clearly attenuated in the densely vegetated Posidonia australis seagrass meadows. Posidonia meadows were generally located beyond the outer margins of the site (i.e. the predicted nutrient discharge area) with the exception of the entrance to Golf Course Lake and Transect E at the northern end of the site (refer Figure 3). Therefore the vast majority of the site is subject to strong tidal flows and due to the shallow depths would be well mixed. In addition to tidal flows, wind advection would also play a role to mix and homogenize the waters overlying the site sediments.

Owing to its wide and deep entrance, Merimbula Lake has exceptionally good tidal flushing and it has been estimated that weekly tidal flows through the entrance are equivalent to approximately twice the total volume of the lake (Webb, McKeown and Associates 1997). Information regarding the tidal prism of Merimbula Lake is available on the NSW Office of Environment and Heritage website (OEH 2013). The tidal prism is the volume of water (cubic metres per second) moving past a fixed cross section of the estuary during each flood tide or ebb tide (i.e. slack water to slack water) (OEH 2013). The tidal prism varies according to tide heights with largest tidal volumes discharged during spring tides. For Merimbula Lake, a tidal prism for a tide of approximately 0.5 mAHD was measured at the causeway on 25 October 2003 (MHL 2003) and is contained in

18

RESULTS AND DISCUSSION

Appendix C. The tidal prism shows that peak discharge of ~140 m3/sec-1 flowed through the causeway during the ebb tide while peak flows during the subsequent flood tide reached ~160 m3/sec-1 . Assuming this tidal prism is representative of an average tide, the volume of lake water transported during average tidal flows may be estimated with moderate confidence (± 20% error) in the absence of real-time data using the tidal prism provided by MHL (2003).

It is estimated that roughly 1,512 ML of lake water was transported through the causeway during the ebb tide with approximately 1,728 ML flowing back through the causeway and into top lake during the flood tide on 25 October 2003 (Table 4). Note that these estimated volumes represent one ebb and one flood tide on the 25 October 2003. Tidal prism will vary throughout the year and on a daily basis due to tidal asymmetry.

Table 4. Estimated tidal discharge at Merimbula causeway, 25 October 2003 (based on coarse analysis of tidal prism MHL 2003).

Estimated Estimated Estimated Estimated total Estimated total average Tide Tide state Tidal volume discharge1 volume discharge discharge duration range (m) (m3 per tide) (ML per tide) (m3/sec-1) (hrs) Ebb flow 60 0.5 7 1,512,000 1,512

Flood flow 80 0.48 6 1,728,000 1,728 Note: 1 Estimated total volume discharge is the product of estimated average discharge x tide duration.

When these estimated discharge volumes are considered with regard to the total volume of the estuary, estimated at 12,924 ML (Roper et al. 2011), a conservative approximation of the number of tidal cycles required to discharge or flush the estuary volume may be estimated by dividing the total lake volume by the tidal discharge volume.

Using the ebb discharge volume (ML),

12,924 / 1,512 = 8.5 tidal cycles (equivalent to 4.3 days) will discharge a volume of water equivalent to the estimated volume of the lake.

Taking a conservative approach, the total volume of Merimbula Lake is likely to be discharged over a 5-day period. However, this is a simplistic interpretation based on the tidal prism data available and assumptions made. Flushing time will vary across the lake areas as well as three dimensionally and while a volume, equivalent to the total lake volume, is likely to be flushed over a 5-day period, this does not mean all lake waters are flushed over that period.

Roper et al. (2011) estimate the flushing time for the entire estuarine water body at 25.3 days based on the predicted tidal prism of 1752 ML, equivalent to 14% of the volume of the lake. This estimate of flushing time adopted a typical tidal exchange efficiency coefficient of 0.15 (Refer Appendix 9 in Roper et al. 2011).

19

RESULTS AND DISCUSSION

Based on the analysis of Roper et al. (2011), it can be assumed that all areas of Merimbula Lake will be flushed over a 25-day period with areas closest to the entrance likely to be flushed over shorter time periods. In absence of three-dimensional modelled data, flushing times for identified areas of Merimbula Lake may be generalised from shortest to longest duration in the following order: • Shortest flushing time - marine tidal delta (incorporating the ‘site’)

• Medium flushing time - central basin

• Longest flushing time - golf course lake backwater

The areas of the lake where these generalised flushing duration times are estimated is shown in Figure 5 below.

Figure 5. Generalised flushing duration periods estimated for areas of Merimbula Lake (i.e. high flushing capacity = shortest duration, low flushing capacity = longest duration).

The area in which nutrients will discharge from the lake-bed is part of the marine-tidal delta and this area is predicted to have a shorter flushing duration (i.e. will be completely flushed over shorter time scale) compared to the central basin and the golf course lake backwater. The volume of water overlying the sediments at the site is estimated to range between 123 and 246 ML based on estimated average depths of 0.3 m and 0.6 m at low and high tide respectively (Table 5). It is likely that the total volume of water overlying the sediments at the site would be completely flushed on a daily basis. This prediction is based on the tidal observations recorded at the site during the field investigation and the estimated volumes of water discharged during an average tidal cycle. However, the degree of tidal exchange is an important consideration with regard to nutrient concentrations and other pollutants and understanding what percentage of estuarine

20

RESULTS AND DISCUSSION

water is exchanged with oceanic water during a range of tidal conditions and what residual estuarine water is retained in the system would require hydrodynamic modeling.

Table 5. Estimated water volumes overlying sediments at the site at mean low and mean high tide.

Site Estimated Estimated Estimated Tide state area average depth Volume Volume (km2) (m) (m3) (ML) Mean Low tide 0.41 0.3 123,000 123

Mean High tide 0.41 0.6 246,000 246 Unit conversions: 1 km2 = 1,000,000 m2, 1 m3 = 0.001 ML

3.2 Current ecological condition of Merimbula Lake An understanding of the current ecological condition of Merimbula Lake is required before a realistic assessment of what potential impacts may result from an increased flux of nutrients and freshwater discharge. Estuarine ecological condition in NSW is currently assessed using 10 indicators representing elements of the structure, function and composition of estuarine ecosystems and are summarised in Table 6 below.

Table 6. Environmental indicators adopted by the state-wide MER program to assess estuarine ecological health (Roper et al. 2011). Issue Indicator

microalgal abundance as phytoplankton determined by chlorophyll a; Eutrophication macroalgal abundance

water clarity as turbidity

extent of seagrass

Habitat Availability extent of mangroves

extent of saltmarsh

species diversity and composition

species abundance Fish Assemblages nursery function

trophic integrity

3.2.1 2010 State of Catchments Report (DECCW 2011) Most recently, a State of the Catchments (SOC) 2010 report (DECCW 2011) was published that provides the latest assessment of ecological condition/health of estuaries and coastal lakes and the pressures acting upon them in the Southern Rivers region including Merimbula Lake. Much of this assessment was based on MER data collected up to 2009. The assessment provided Merimbula Lake with an overall condition index of 3.3 (out of 5), rated as being fair based on four

21

RESULTS AND DISCUSSION

of seven estuarine health indicators applicable to Merimbula Lake. Levels of chlorophyll a were rated as good, extent of seagrass and fish assemblages rated as fair, and extent of saltmarsh rated as poor. The overall assessment was provided with medium confidence as some of the data was greater than three years old and data regarding turbidity or macroalgae was not available.

The assessment also provided Merimbula Lake with an overall pressure index of 3.0 (out of 5), rated as having moderate pressure in terms of indicators – cleared land, population, sediment and nutrient inputs, extractive fishing, freshwater flows, disturbed habitat and tidal flows. Among the indicators considered, nutrient inputs, disturbed habitat and tidal flows were rated as moderate pressures while cleared land, population and sediment inputs were deemed to be exerting the highest pressure on the condition of the estuary.

3.2.2 Surface Water Quality of Merimbula Lake Ecological condition is also largely determined by water quality. Consistent high levels of nutrients may create conditions for prolific micro- and macroalgal growth, diminishing water clarity and affecting the ability of seagrass meadows to function efficiently. Seagrass meadows are a critical component of estuarine systems, and loss of seagrass habitat may have consequences at higher trophic levels. Background levels of nutrients for surface waters of Merimbula Lake are available for the central basin, golf course lake backwater and the ocean entrance. Mean values for a range of nutrient parameters, chlorophyll a and indicators of water clarity are summarised in Table 7.

The central basin is characterised by low mean nutrient concentrations typically well below the guidelines for the protection of aquatic ecosystem health. Mean levels of chlorophyll a range from 1.1 to 1.3 µg/L and water clarity is very high with turbidity less than 0.5 ntu. In contrast, Golf Course Lake is characterised by higher mean nutrient levels with some bioavailable forms of nitrogen exceeding guideline values. Consequently, Golf Course Lake has a higher abundance of microalgae (as indicated by chl a) and diminished water clarity compared to the central basin. This water quality data supports the prediction (Figure 5, above) that Golf Course Lake is not as well flushed and has longer water residence times than the central basin and the marine tidal delta. The data also support anecdotal reports from oyster growers that highest oyster growth rates can be achieved in Golf Course Lake owing to the higher microalgal biomass.

Overall, water quality of the estuary is considered high with low nutrient levels and high water clarity largely due to the lake’s high flushing capacity that allows waters to be well mixed over most areas of the lake.

22

RESULTS AND DISCUSSION

Table 7. Mean water column nutrients and properties for Merimbula Lake (note - shaded mean values indicate guideline value has been exceeded)

+ NH4 NOx TKN TN TP FRP Chl a TSS Turbidity (µg/L) (µg/L) (µg/L) (µg/L) (µg/L) (µg/L) (µg/L) (mg/L) (ntu)

ANZECC guideline1 15 15 - 300 30 5 4 - 0.5-10

MER guideline2 ------3.6 - 5.7

Central Basin3 7.6 17 175 196 9 2.4 1.1 - 0.2

Central Basin4 ~28 - - 223 9 - 1.3 18 -

Golf Course Lake4 ~50 - - 393 28 - 3.4 31 -

Entrance5 - - - 194 - - 2.7 1.4 -

Note: 1 WQOs for protection of Estuarine Aquatic Ecosystems in Bega River Catchment - based on ANZECC/ARMCANZ 2000 guidelines (http://www.environment.nsw.gov.au/ieo/Bega/index.htm) for slightly disturbed ecosystems in SE Australia (ANZECC Table 3.3.2) 2 Chlorophyll a and turbidity trigger level adopted by the NSW MER program (Roper et al. 2011) 3 Mean values calculated from 2012 data (Elgin Associates 2013) 4 Mean values calculated from 2005-2008 data (BVSC 2013) 5 Mean values calculated from 2002 data (Ozcoasts 2013)

23

RESULTS AND DISCUSSION

3.3 Response of vegetation communities to increased nutrient flux The primary concern with the worst case modeled increase in nutrient flux and freshwater discharge from the lake bed is whether that will have a negative impact on the ecological values of the lake over the life of an exfiltration trench. An assessment of factors that could influence potential impact is discussed in the sections below in terms of how the vegetation communities may respond to increased nutrient flux and freshwater discharge.

3.3.1 Nutrient limitation Nitrogen is widely considered to be the limiting nutrient for plant and algal growth in the marine and estuarine environment and a large body of evidence now supports this trend (Lobban and Harrison 1994, Howarth and Marino 2006, Smith 2006), with P the second most limiting nutrient (Lobban and Harrison 1994). Consequently, efforts to minimise the effects of eutrophication in coastal areas have focused on the management of N inputs. In contrast, P is the limiting nutrient in freshwater systems and excess inputs of P are typically the cause for eutrophication and algal blooms, commonly of cyanobacterial taxa that have the capacity to fix atmospheric nitrogen (N2).

Understanding the nutrient demands of a plant or algae will help to predict its response to increased nutrient availability. A desktop review of literature regarding the physiology of algae and of specific studies investigating the responses of seagrass and saltmarsh to increased nutrients allow some general predictions to be considered here.

The nutrient demands (ratio of N:P) required by one plant or algal species may be quite different from the nutrient ratio required by another species. One species may be N-limited, while another species may be P-limited. The nutrient supply rate is also important in determining the magnitude or degree of nutrient limitation. If the concentration of a nutrient is low, but the supply rate is slightly less than the uptake rate by the plant or algae, then the plant or algae will only be slightly limited. Furthermore, the rates of nutrient turnover by a species and capacity to store nutrients will also influence how a species may respond to increased nutrient availability.

In general, model predictions by IGCC (2013) for the worst case scenario indicate that effluent disposal to an exfiltration trench in the location shown in Figure 1 would result in addition of N and P nutrients and freshwater to receiving Lake waters at the site. Under scenarios modelled by

IGCC, steady state concentrations of N (scenarios 2 and 4 - mostly as bioavailable NO3) and P

(scenarios 2 and 4 - mostly as bioavailable PO4) were predicted to be discharged from the lake bed after 15 to 22 years, respectively. For all of these scenarios, efficient tidal flushing will effectively dilute and reduce these concentrations and transport nutrients to other regions of the lake. However, this discharge of nutrients from sediment porewater would represent a new continuous supply of inorganic N and P in bioavailable forms that would have the potential to further stimulate existing levels of primary production within the lake. For the different ecological communities identified at the site, their limitation to N or P nutrients are noted where information from the literature was available.

3.3.2 Benthic and Pelagic microalgae Benthic microalgae comprising mostly of diatoms but also of other taxa including marine cyanobacteria contribute a significant fraction of the total primary production in estuarine

24

RESULTS AND DISCUSSION

systems where water clarity is high. They form biofilms over the sediment surface binding sediment particles and stabilise sediments against erosion. In this way, benthic microalgae can influence estuarine morphology. Aggregations of benthic microalgae were conspicuous at the southern end of the site around faunal burrows though they would be present across the entire site. Diatom nutrient requirements generally follow the Redfield ratio of elements carbon, nitrogen and phosphorous (C:N:P), which is 106:16:1 (by atoms). Therefore in an environment where supplies of inorganic N and P are continuous, enhanced productivity of benthic microalgae may result, and a large proportion of available nutrients assimilated.

Pelagic microalgae would be transient at the site due to the strong tidal flows. However, as nutrient concentrations would be diluted and transported away from the site on a daily basis, increased phytoplankton biomass may become evident in other areas of the estuary where water residence times are longer such as the central basin and Golf Course Lake. As microalgal abundance of lake surface waters is typically low (chlorophyll a mean concentrations of 1.1- 1.3 µg/L), a response by the pelagic microalgal community to further nutrient inputs would be measurable as chlorophyll a concentrations above current background levels.

3.3.3 Macroalgae The occurrence of macroalgae at the site is limited by available hard substrates for attachment. Consequently, majority of macroalgal taxa at the site are epiphytic on the leaf blades of seagrasses with the most dominant species being small and filamentous (Centroceras, Polysiphonia, Spyridia, Laurencia). A filamentous thallus provides a high surface area: volume ratio and filamentous algae typically have a high propensity for nutrient uptake and fast growth rates (Lobban and Harrison 1994). The epiphytic species observed during the site inspection were annual species with a preference for growth in spring to summer and disappearing altogether during the cooler seasons. In contrast, larger perennial algae observed at the site such as Hormosira, Codium, and Cystoseira would be present throughout the year. These types of algae are slow growing species that have a greater capacity to store nitrogen though their local abundance at the site is limited due to a lack of available hard substrate.

An increased nutrient flux to the site and a continuous supply of inorganic nutrients more generally will favour the growth of fast growing macroalgae, typically of filamentous or foliose forms, that can grow attached to seagrasses. As such, epiphytic loads on seagrasses are likely to increase at the site throughout the year. The ability of seagrass to photosynthesise may be directly affected by increased epiphyte loads through shading.

Prolific growth of two macroalgal taxa is already known to occur in Merimbula Lake on a seasonal basis. Blooms of the brown alga Colpomenia sinuosa have occurred each winter since 2007 (N. Yee, pers. obs. 2007-2012). The alga grows attached to the leaf blades of Posidonia until it reaches a size that cannot resist the drag forces of tidal flows and is torn from its seagrass substrate. Thalli of Colpomenia wash up along the shoreline of the lake in early summer and are further washed out to Merimbula Bay where it aggregates on the seafloor and begins to decompose. Blooms of the finely branched calcareous alga Jania micrarthrodia have been reported in summer though on an irregular basis. Jania is also an epiphyte of Posidonia and once detached from the seagrass may be transported from the lake to the bay environment during ebb tidal flows where large biomass

25

RESULTS AND DISCUSSION

aggregate on the seafloor. Aggregations of drift algae were not present at the site due to the strong tidal flows and an increase in nutrient flux will not alter this. However, short-term aggregations of drift algae may occur in slow flow areas of the lake before being flushed out of the estuary altogether. Images of these algal taxa forming blooms in Merimbula Lake are contained in Appendix D.

The triggers that cause the prolific growth of Colpomenia and Jania are not understood. However, the regular seasonal occurrence of blooms in Merimbula Lake suggest any additional inputs to existing levels of nutrients may encourage the prolific growth of other algal taxa whose nutrient demands are not currently being addressed.

3.3.4 Saltmarsh There have been few studies in Australia that have examined the responses of temperate coastal saltmarsh to nutrient enrichment. However, a number of long-term studies in America have shown that nutrient enrichment to Spartina (smooth cordgrass) coastal wetlands resulted in an overall loss of wetland vegetation (Deegan et al. 2012). For most plants increased N generally stimulates higher rates of leaf growth and development, while P is more important for the production of flowers and fruiting. Deegan et al. (2012) demonstrated that nutrient enrichment resulted in increased above ground plant-biomass, with a concomitant decrease or no-change to below ground biomass. The increased leaf matter subsequently results in higher rates of microbial decomposition of the organic matter within the sediments. The combination of root loss and increased rates of microbial decomposition reduced soil strength that led to increased erosion during tidal flows. This resulted in reduced geomorphic stability, creek bank collapse and overall losses of Spartina habitat that was replaced by large areas of unvegetated mud. However, the saltmarsh communities of southern Australia are very different floristically to the Spartina coastal wetlands of the northern hemisphere.

A study by Boon and Cain (1988) examined the sediments and rates of nitrogen cycling in a samphire (Sarcocornia) saltmarsh community in southern Australia. The sediments were found have a very high inorganic N:P ratio (>100:1) suggestive of a high limitation of bioavailable phosphate in that setting. The rate of nitrogen cycling during the decomposition of plant matter (i.e. conversion of organic nitrogenous compounds to inorganic bioavailable forms) is closely linked to the presence of P in freshwater sediments (Sjogren and Little 1982) and a similar situation may exist in marine settings (Boon and Cain 1988). Assuming saltmarsh sediments at the site are also characterised by a high N:P ratio, an increased liberation of inorganic nitrogen to stimulate further plant growth may result from increased levels of phosphate in shallow groundwater. The resultant higher primary productivity of the saltmarsh may feedback and in turn alter saltmarsh sediment chemistry where the ratio of inorganic N:P is lowered with an associated increase in organic content. With forecast rise in sea levels, an organic-rich sediment with higher levels of inorganic P may favour the encroachment of mangroves into the saltmarsh area.

An increased discharge of freshwater to the saltmarsh may lead to more brackish water conditions providing less saline-tolerant saltmarsh species opportunities to establish or expand their distribution.

26

RESULTS AND DISCUSSION

3.3.5 Seagrass The seagrass landscape of Merimbula Lake consists of three species: Posidonia australis, Zostera marina and Halophila ovalis. All three seagrasses are present at the site in various patch sizes and shoot densities with Posidonia confined to the deeper water margins of the site while Halophila and Zostera occupy the shallow, near shore areas where nutrient flux is expected to be greater. Seagrasses obtain majority of their nutrients from the sediments via the roots, though they are also able to uptake inorganic N from the water column through their leaves (Pedersen et al. 1997, Gobert et al. 2005) and highest rates of productivity (i.e. nutrient uptake) typically occur during the warmer months. The nutrient requirements of seagrasses is similar to that of macroalgae, with a C:N:P ratio of approximately 480:27:1 (Eyre and Ferguson 2002). In a temperate estuarine environment with sandy sediments where inorganic P is accessible, it is the availability of nitrogen that generally limits the growth of seagrasses.

Local seagrass productivity would benefit from an increased flux of both inorganic N and P, though the proportion of nutrients assimilated by seagrasses would likely be less than the total proportion assimilated by faster growing algal species including the benthic and pelagic microalgae, and macroalgal epiphytes. Declines in seagrass habitat have occurred around the world due to competition with algae for resources, shading effects due to epiphyte loads and indirectly through reduced light levels in the water column associated with increased phytoplankton biomass (Collings et al. 2006). However, the primary concern for seagrass at the site is direct competition with algae for nutrients and potentially greater epiphyte loads. Water clarity is expected to remain high due to the strong tidal flows at the site. 3.4 Local case study of increased nutrient supply to an estuarine setting

Racecourse Creek is a shallow backwater section of the Bega River estuary where flushing and water movement is restricted. Coincidentally, Racecourse Creek is also adjacent to sources of continual nutrient input via surface runoff from the Tathra golf course that uses reclaimed water from the Tathra STP as well as groundwater discharge characterised by elevated levels of nutrients. In 2008, an extensive mixed species macroalgal bloom was present in Racecourse Creek covering as much as 50% of the waterbody (Elgin Associates 2009). Over 14 algal taxa were recorded from the bloom with dominant bloom species including the green algae Ulva intestinalis (as Enteromorpha intestinalis) and Chaetomorpha valida, and the blue-green alga Oscillatoria sp. (Elgin Associates 2009). The seagrass in Racecourse Creek had heavy epiphyte loads and were completely smothered either by surface rafts or by decomposing sub-surface algal rafts. Persistent smothering as observed in 2008 would have a negative outcome for the seagrass in the long-term. Water quality data collected during 2008 showed that high levels of bioavailable forms of N and P were present throughout the year and combined with low tidal flushing due to river entrance closure/restriction, presented ideal conditions for the development and persistence of blooms of opportunistic and fast growing algal species.

Widespread blooms of opportunistic algal taxa are not unlikely to be realised at the site due to the high degree of tidal flushing. However, Golf Course Lake is an area of the estuary that is vulnerable to increased nutrient concentrations due to its reduced capacity for flushing. During flood tides a proportion of water flowing across the site would be transported into Golf Course

27

RESULTS AND DISCUSSION

Lake in addition to shallow groundwater discharge. The backwater would be supplied with regular pulses of nutrients in bioavailable forms to feed the growth of algae and seagrasses.

28

CONCLUSIONS

4 CONCLUSIONS This supplementary report provides information regarding the vegetation communities at the site and discussion of thepotential impacts that proposed dunal exfiltration may have on the ecological values of Merimbula Lake. This information includes:

• Confirmation of and description of vegetation communities at the site;

• Qualitative discussion regarding the hydrodynamics of Merimbula Lake;

• The current ecological condition and surface water quality of Merimbula Lake;

• Factors that could influence the response of vegetation communities to increased nutrient flux; and

• Local case study of increased nutrient supply to an estuarine setting.

Key points from the findings include:

• A range of ecological communities is present at the site including saltmarsh, mangrove, intertidal sand flats, and seagrass meadows. Three seagrasses occur at the site including Posidonia, Zostera and Halophila. Estuarine habitat mapping (Creese et al. 2009) of Merimbula Lake accurately depicts the current distribution of Posidonia at the site but underestimates the distribution of Halophila and Zostera which occur over much of the shallow waters depicted in mapping as being unvegetated. Overall, it is estimated that a seagrass landscape (including sparse and dense meadows) may cover as much as 0.25 km2, or approximately 60% of the site as defined in Figure 2.

• A variety of macroalgae were encountered during the site inspection with majority being epiphytes of seagrass. Leaf blades of seagrasses represent the most abundant available substrate for colonisation by macroalgae. The dominant epiphytic taxa on seagrass included four species of red algae (Laurenica majuscula var. elegans, Centroceras clavulatum, Spyrida filamentosa and Polysiphonia infestans) and two species of brown algae (Dictyota alternifida and Dictyota dichotoma) representing the summer epiphyte flora. In winter, the dominant epiphyte is known to be the brown alga Colpomenia sinuosa that has shown prolific growth in winter each year since (at least) 2007. The calcareous red alga Jania micrarthrodia is also known to proliferate in Merimbula Lake on an irregular seasonal basis.

• The availability of natural hard substrates for algal attachment was limited to a small area in the form of an exposed shell bed. Larger perennial macroalgal species such as the brown algae Cystoseria and Hormosira and the green alga Codium occurred in this area. In addition to macroalgae, aggregations of benthic microalgae were noted on the sandy sediments associated with faunal burrows. At high densities, burrowing fauna may be the dominant process of porewater advective exchange (Santos et al. 2012). This could be an important mechanism for enhancing the release of nutrients from the lake bed to be flushed away from the immediate site by tidal currents.

• Merimbula Lake has a high capacity for tidal flushing due to its wide and deep ocean entrance that promotes efficient tidal exchange and mixing of lake waters. It is estimated that weekly tidal flows through the entrance are equivalent to approximately twice the total volume of the lake (Webb, McKeown and Associates 1997). Strong tidal flows were observed

29

CONCLUSIONS

over the sand flats at the site with flows attenuated over the Posidonia seagrass meadows. The site is part of the marine tidal delta and it is predicted that the site would be completely flushed on a daily basis effectively diluting and transporting nutrients discharged from sediments away from the site.

• The current ecological condition of the Lake based on MER indicators of eutrophication - microalgal abundance (as chlorophyll a) and water clarity (as turbidity) is rated as good. Surface water quality data collected over all seasons from 2005-2008 and 2012 show water clarity is consistently high with turbidity typically less than 0.5 ntu. Nutrient levels of the central basin are typically low and consequently microalgal abundance is also low with mean concentrations of chlorophyll a between 1.1-1.3 µg/L. However, surface water quality data show levels of nutrients and microalgae are higher in the backwater of Golf Course Lake likely due to the longer water residence times in this area of the estuary.

IGGC (2013) groundwater flow mass balance modelling for year 2025 estimated effluent disposal volumes via a 400 metre long exfiltration trench in the location shown in Figure 1 predicts a net increase in groundwater discharge to Merimbula Lake of approximately 7.5%, occurring within an area of approximately 28,000 m2 on the eastern side of the lake. Under scenarios modelled by

IGCC, steady state concentrations of N (scenarios 2 and 4 - mostly as bioavailable NO3) and P

(scenarios 2 and 4 - mostly as bioavailable PO4) were predicted to be discharged from the lake bed after 15 to 22 years, respectively. Under scenarios 1 and 3 neither nitrate nor phosphate from effluent reach the lake in groundwater within the 57 year modeled period.

For scenarios 2 and 4, tidal flushing will dilute and reduce the concentrations of nitrogen and phosphorous discharging within groundwater within the identified discharge plume area and transport these nutrients to other regions of the lake. Nevertheless, this discharge of nutrients from sediment porewater would represent a new continuous supply of inorganic N and P in bioavailable forms that has the potential to further stimulate existing levels of primary production at the site and within the lake generally. A potentially vulnerable area of the lake to increased supply of bioavailable nutrients is the backwater Golf Course Lake due to its reduced capacity for flushing and estimated longer water residence times.

30

REFERENCES

5 REFERENCES Boon, P.I. and Cain, S. (1988). Nitrogen cycling in salt-marsh and mangrove sediments at Wetsern Port, Victoria. Aust. J. Mar. Freshwater Research, 39: 607-623.

BVSC (2013). Water quality data for Merimbula Lake and Golf Course Lake – 2005 to 2008 (unpubl.).

Collings, G., Bryars, S., Nayar, S., Miller, D., Lill, J and O’Loughlin, E. (2006). Elevated nutrient responses of the meadow forming seagrasses, Amphibolis and Posidonia, from the Adelaide metropolitan coastline. ACWS Technical Report No. 11. Prepared for the Adelaide Coastal Waters Study Steering Committee. South Australian Research and Development Institute (Aquatic Sciences) Publication No. RD01/0208-16, Adelaide.

Creese, R.G., Glasby, T.M., West, G. and Gallen, C. (2009). Mapping the habitats of NSW estuaries. Report to the Hunter Central Rivers Catchment Management Authority, September 2009. Available online at URL: http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0004/306625/AE_2009_Output- 1575_Creese-et-al_Habitat-Mapping-Final-Report-113_REPORT.pdf

DECCW (2011). State of the catchments 2010 Estuaries and Coastal Lakes – Southern Rivers region. Available online at URL: http://www.environment.nsw.gov.au/resources/soc/southernrivers/10603SRestuarine.p df

Deegan, L.A., Johnson, D.S., Warren, R.S., Peterson, B.J., Fleeger, J.W., Fagherazzi, S. and Wollheim, W.M. (2012). Coastal Eutropication as a driver of saltmarsh loss. Nature, 490: 388-394.

Elgin Associates (2009). Algal Bloom and Water quality Assessment: Racecourse Creek, Bega River estuary 2008. Report prepared for BVSC, 10 September 2009. Re-issued with corrections, 14 July 2011.

Elgin Associates (2013). Environmental monitoring of coastal lakes and lagoons in the BVSC region: Merimbula Lake 2012. (in prep).

Eyre, B.D. and Ferguson, A.J.P. (2002). Comparison of carbon production and decomposition, benthic nutrient fluxes and denitrification in seagrass, phytoplankton, benthic microalgae- and macroalgae dominated warm-temperate Australian lagoons. Mar. Ecol. Prog. Series: 229: 43-59.

Gobert, S., Lejeune, P., Lepoint, G., Bouquegneau, J. (2005). C, N, P concentrations and requirements of flowering Posidonia oceanica Shoots. Hydrobiologia 533: 253-259.

IGGC (2013). Disposal of STP Effluent by Dunal Exfiltration – Investigation and Assessment of Impacts on Groundwater and Merimbula Lake and Bay. Report prepared for BVSC, February 2013.

MHL (2003). Merimbula Lake – 25 October 2003. Manly Hydraulics Lab, MHL Report 1290.

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REFERENCES

OzCoasts (Geoscience Australia) (2013). Estuary Search (webpage) – Merimbula Lake water quality data. Viewed 14 January 2013. URL: http://www.ozcoasts.gov.au/search_data/estuary_search.jsp

OEH (2013). Estuaries of NSW – Merimbula Lake. URL: http://www.environment.nsw.gov.au/estuaries/stats/MerimbulaLake.htm, accessed January 2013.

Pedersen, M.F., Paling, E.I. and Walker, D.I. 1997. Nitrogen uptake and allocation in the seagrass Amphibolis antarctica. Aquatic Botany 56 : 105-117.

Roper T., Creese B., Scanes P., Stephens K., Williams R., Dela-Cruz J., Coade G. and Coates B. (2011) Assessing the condition of estuaries and coastal lake ecosystems in NSW. Office of Environment and Heritage, Sydney).

Lobban, C.S. and Harrison, P.J. (1994). Seaweed ecology and physiology. Cambridge University Press 1994, New York, U.S.

Howarth, R. W. and Marino, R. (2006). Nitrogen as the Limiting Nutrient for Eutrophication in Coastal Marine Ecosystems: Evolving Views over Three Decades. Limnology and Oceanography, Vol. 51, No. 1, Part 2: Eutrophication of Freshwater and Marine Ecosystems (Jan., 2006), pp. 364-376.

Santos, I.R., Eyre, B.D. and Huettel, M. (2012). The driving forces of porewater and groundwater flow in permeable coastal sediments: A review. Estuarine, Coastal and Shelf Science 98: 1- 15.

Smith, V. (2006). Responses of Estuarine and Coastal Marine Phytoplankton to Nitrogen and Phosphorus Enrichment. Limnology and Oceanography, Vol. 51, No. 1, Part 2: Eutrophication of Freshwater and Marine Ecosystems (Jan., 2006), pp. 377-384.

Webb, McKeown and Associates (1997). Merimbula Lake and Back Lake Estuary Management Plan and Management Study Summary. Prepared for BVSC, January 1997.

32

LIMITATIONS

6 LIMITATIONS Elgin Associates Pty Ltd has prepared this report for the sole use of Bega Valley Shire Council in accordance with the usual care and thoroughness of the consulting profession. It is based on generally accepted practices and standards at the time it was prepared. No other warranty, expressed or implied, is made as to the professional advice included in this report. It is prepared in accordance with the scope of work and for the purpose outlined in the Proposal dated 28 November 2012.

The methodology adopted and sources of information used by Elgin Associates are outlined in this report. Elgin Associates has made no independent verification of this information beyond the agreed scope of works and Elgin Associates assumes no responsibility for any inaccuracies or omissions. No indications were found during our investigations that information contained in this report as provided to Elgin Associates was false.

This report was prepared between December 2012 and March 2013 and is based on the conditions encountered and information reviewed during that period up to the time of preparation. Elgin Associates disclaims responsibility for any changes that may have occurred after this time. Opinions and recommendations contained in this report are based upon information gained during desktop study and fieldwork and information provided from government authorities’ records and other third parties. The information in this report is considered to be accurate at the date of issue and reflects at the site at the dates sampled. This document and the information contained herein should only be regarded as validly representing the site conditions at the time of the fieldwork unless otherwise explicitly stated in a preceding section of this report.

This report should be read in full together with all other reports referenced by this report. No responsibility is accepted for use of any part of this report in any other context or for any other purpose or by third parties.

33

ATTACHED TABLES

Table 3. Macroalgae recorded during the site inspection

ATTACHED TABLES

Table 3. Macroalgae recorded during the site inspection and other taxa recorded in Merimbula Lake but not observed at the site.

Recorded in Taxon Notes Transect Red algae (Phylum Rhodophyta) Laurencia majuscula var. elegans A, B, C, D, E A conspicuous red alga, highly branched, epiphytic on Posidonia australis seagrass. Abundant. Centroceras clavulatum A, B, C, D, E A small, filamentous red, epiphytic on Halophila and Zostera seagrass. Abundant. Spyridia filamentosa A, B, C, D, E A filamentous red alga, epiphytic on all seagrasses. Common. Polysiphonia infestans A, B, C A small filamentous red alga, epiphytic on all seagrasses. Abundant. Polycerea nigrescens* - A small filamentous red alga, epiphytic on Posidonia. Jania micrarthrodia* - A finely branched, calcareous red alga, epiphytic on Posidonia. Common in spring and summer. Brown algae (Class Phaeophyceae) Dictyota alternifida A, B Commonly found attached to shell fragments or epiphytic on Posidonia australis, Halophila ovalis seagrass. Dictyota dichotoma A Commonly found attached to shell fragments or epiphytic on Posidonia australis, Halophila ovalis seagrass. Hormosira banksii A, B, Intertidal and shallow sub-tidal. Attached to shell fragments and also unattached, scattered amongst seagrass. Epiphyte of Posidonia seagrass. Found throughout the lake where Posidonia grows and blooms in winter to Colpomenia sinuosa E early spring. Proliferates annually during winter. Cystoseira trinodis B, C A large conspicuous species attached to shell fragments, common in shallow waters at the site. Sargassum sp.* - A Asperococcus bullosus* - A membranous brown alga with an elongate and hollow thallus, epiphytic on Posidonia seagrass. Green algae (Phylum Chlorophyta) Codium fragile B, C Attached to rock, shells, and oyster lease infrastructure. Note: * Commonly recorded in Merimbula Lake though not encountered at the site on 21 December 2012.

ATTACHED FIGURES

Figure 2. Study Site

Figure 3. Estuarine vegetation and survey transects inspected

Figure 4. Survey Transects

APPENDIX A

IGGC (2013) - Figures 13.11a – 13.11f

Disposal of STP Effluent by Dunal Exfiltration Investigation and Assessment of Impacts on Groundwater and Merimbula Lake and Bay

Figure 13.11a: Phosphate Concentrations in Groundwater, Scenario 1 (High Effluent

PO4=8.5 mg/L; Low P Sorption Capacity, Kd=2.0 mL/g)

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Figure 13.11b: Phosphate Concentrations in Groundwater, Scenario 2 (High Effluent

PO4=8.5 mg/L; Very Low P Sorption Capacity, Kd=0.1 mL/g)

Ian Grey Groundwater Consulting Pty Ltd FJ06/Rp056 Rev D Page 141

Disposal of STP Effluent by Dunal Exfiltration Investigation and Assessment of Impacts on Groundwater and Merimbula Lake and Bay

Figure 13.11c: Phosphate Concentrations in Groundwater, Scenario 3 (Low Effluent

PO4=1.5 mg/L; Low P Sorption Capacity, Kd=2.0 mL/g)

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Figure 13.11d: Phosphate Concentrations in Groundwater, Scenario 4 (Low Effluent

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Ian Grey Groundwater Consulting Pty Ltd FJ06/Rp056 Rev D Page 142

Disposal of STP Effluent by Dunal Exfiltration Investigation and Assessment of Impacts on Groundwater and Merimbula Lake and Bay

Figure 13.11e: Nitrate Concentrations in Groundwater, Scenarios 1 and 3 (Moderate N Decay Rate Constant R=0.002 day-1)

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Figure 13.11f: Nitrate Concentrations in Groundwater, Scenarios 2 and 4 (Zero N Decay Rate Constant R=0 day-1)

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Ian Grey Groundwater Consulting Pty Ltd FJ06/Rp056 Rev D Page 143

APPENDIX B

Images from Field Inspection, 21 December 2012

Plate 1. Mangrove and Saltmarsh habitat

Plate 2. Transects A1 and A2 – entrance to backwater

Plate 3. Transect B – natural hard substrates

Plate 4. Seagrass epiphyte loads at Transects A & B – southern end of site

Plate 5. Seagrasses at Transects C, D & E – northern end of the site

Plate 6. Micrographs of macroalgal epiphytes on segrasses

APPENDIX B

Plate 1. Mangrove and Saltmarsh habitat a) A band of the grey mangrove (Avicennia marina) occupy the high intertidal zone along the entire lakeshore at the site. b) Mangrove leaf litter, pneumatophores (specialised root structures) and drift algae are found below the mangrove canopy. c) Mangrove sediments are typically grey in colour, contain high silt and organic content relative to the estuarine sand flats and have a sulphide odour when disturbed. Faunal burrows are common in the mangrove sediments created by range of invertebrates including the red-fingered marsh crab (Sesarma erythrodactyla). d) Saltmarsh plants occupy the higher ground immediately behind the band of mangroves with samphire (Sarcocornia quinqueflora) common. e) Narrow bands of coastal speargrass (Austrostipa stipoides) and sea rush (Juncus krausii) are found immediately behind the mangroves and along the drainage channels. f) Shrubby samphire (Tecticornia arbuscula), a medium sized shrub is the most conspicuous saltmarsh plant at the site.

APPENDIX B

Plate 2. Transects A1 and A2 – entrance to backwater a) Large areas of sand flats become exposed at low tide at the entrance to the backwater. b) The view South overlooking the main channel that opens into a deeper backwater section of Merimbula Lake that is adjacent to the Merimbula golf course and the Merimbula STP. c) The large seagrass Posidonia australis is abundant throughout the main channel that acts to slow the velocity of tidal flows. d, e) Epiphyte loads (of macroalgae) on the leaf blades of Posidonia australis appear to be greater in the vicinity of Transect A1 and A2 compared to other areas of the site. e) A close-up image of the red alga Laurencia sp., a common epiphyte of Posidonia australis throughout Merimbula Lake. f) The smaller seagrass Halophila ovalis is also widespread in this area covered with macroalgal epiphytes and drift algae such as Hormosira banksia.

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APPENDIX B

Plate 3. Transect B – natural hard substrates a, b) Exposed shell beds in the vicinity of Transect B represent the only natural hard substrata at the site. Larger brown macroalgae such as Sargassum spp. and Cystoseira trinodis are common in the subtidal zone of this area attached to the dead shells. c, d) The exposed shell beds extend from the shallow subtidal zone to the intertidal zone where oysters have naturally recruited to form large clumps. e) The brown alga Hormosira banksii, is abundant among the mangrove roots along the lakeshore in vicinity of Transect B. f) The shallow sand flats are characterised by faunal burrows and evidence of bio-turbation. Aggregations of benthic microalgae (dark green patches in photo) were conspicuous around the entrance of some burrows.

APPENDIX B

Plate 4. Seagrass epiphyte loads at Transects A & B – southern end of site a, b) The seagrass landscape of shallow waters at the site is composed predominantly of the smaller paddleweed (Halophila ovalis) and stunted eelgrass (Zostera muelleri). Seagrasses at the southern end of the site are affected by heavier loads of macroalgal epiphytes compared to the northern end of the site. c) Close-up image of fine filamentous epiphytes on paddleweed leaf blades. Dominant epiphytes included the red algae Centroceras clavulatum, Polysiphonia infestans and Spyridia filamentosa. d) Larger brown algae including Dictyota dichotoma and Dictyota alternifida (circled) were also common epiphytes of seagrasses at the southern end. e, f) The broad leaf blades of Posidonia australis were characterised by moderate to heavy loads of macroalgal epiphytes, mostly of the red alga Laurenica sp.

APPENDIX B

Plate 5. Seagrasses at Transects C, D & E – northern end of the site a, b) The large seagrass Posidonia australis had relatively light epiphyte loads in the vicinity of Transects C, D and E compared to Transects A and B. c) The brown alga Colpomenia sinuosa was a common epiphyte of Posidonia leaf blades in the deeper waters at the northern end of the site. d) The seagrass landscape of paddleweed (Halophila ovalis) and eelgrass (Zostera muelleri) generally had lighter loads of macroalgal epiphytes at northern end of site. e, f) Large areas of benthos surveyed at Transects C, D and E comprised sparse patches of seagrass with larger seaweeds such as Cystoseira trinodis occasionally present. A number of sea hares (Aplysia sydneyensis) were grazing at the northern end of site (Image E).

APPENDIX B

Plate 6. Common macroalgal epiphytes of seagrasses at the site a-d) Red alga Centroceras clavulatum. Images show the mass of microscopic erect filaments attached to the seagrass leaf blade (a), by a network of prostrate filaments and rhizoids (b). Branches are dichotomously branched with involute apices and a ring of pericentral cells gives the alga a banded appearance. e & f) Red alga Polysiphonia infestans. Images show reproductive tetrasporangia developing in spiral series along an upper branch of a tetrasporophyte (e), and spermatangial branches developing near the branch apex of a gametophyte (f).

APPENDIX C

Merimbula Lake Tidal Prism 25 October 2003, at Causeway

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MHL MERIMBULA LAKE Report 1988 Figure 25 OCTOBER 2003 57

DRAWING 1988-57.CDR APPENDIX D

Examples of macroalgal blooms in Merimbula Lake

APPENDIX D

Plate 1. Macroalgae known to proliferate seasonally in Merimbula Lake a, b) The finely branched and articulated coralline red alga Jania micrathrodia (bleached white in images – typically a light pink colour) has been known to proliferate in shallow, slow flow areas of Merimbula Lake during early summer where its primary substrate for attachment are the leaf blades of the seagrass Posidonia australis (photos taken in January 2011).

c, d) The membranous brown alga Colpomenia sinuosa proliferates during winter in Merimbula Lake where it becomes the dominant epiphyte on the seagrass Posidonia australis (photos taken in September 2008). Once the alga reaches a large size it is typically torn from its substrate due to the drag forces of the tidal flows and washes up along the shoreline of the lake or further washed out to Merimbula Bay.